UXP/toolkit/mozapps/extensions/AddonManager.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

const Cc = Components.classes;
const Ci = Components.interfaces;
const Cr = Components.results;
const Cu = Components.utils;

// Cannot use Services.appinfo here, or else xpcshell-tests will blow up, as
// most tests later register different nsIAppInfo implementations, which
// wouldn't be reflected in Services.appinfo anymore, as the lazy getter
// underlying it would have been initialized if we used it here.
if ("@mozilla.org/xre/app-info;1" in Cc) {
  let runtime = Cc["@mozilla.org/xre/app-info;1"].getService(Ci.nsIXULRuntime);
  if (runtime.processType != Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT) {
    // Refuse to run in child processes.
    throw new Error("You cannot use the AddonManager in child processes!");
  }
}


const PREF_BLOCKLIST_PINGCOUNTVERSION = "extensions.blocklist.pingCountVersion";
const PREF_DEFAULT_PROVIDERS_ENABLED  = "extensions.defaultProviders.enabled";
const PREF_EM_UPDATE_ENABLED          = "extensions.update.enabled";
const PREF_EM_LAST_APP_VERSION        = "extensions.lastAppVersion";
const PREF_EM_LAST_PLATFORM_VERSION   = "extensions.lastPlatformVersion";
const PREF_EM_AUTOUPDATE_DEFAULT      = "extensions.update.autoUpdateDefault";
const PREF_EM_STRICT_COMPATIBILITY    = "extensions.strictCompatibility";
const PREF_EM_CHECK_UPDATE_SECURITY   = "extensions.checkUpdateSecurity";
const PREF_EM_UPDATE_BACKGROUND_URL   = "extensions.update.background.url";
const PREF_APP_UPDATE_ENABLED         = "app.update.enabled";
const PREF_APP_UPDATE_AUTO            = "app.update.auto";
const PREF_MATCH_OS_LOCALE            = "intl.locale.matchOS";
const PREF_SELECTED_LOCALE            = "general.useragent.locale";
const UNKNOWN_XPCOM_ABI               = "unknownABI";

const UPDATE_REQUEST_VERSION          = 2;
const CATEGORY_UPDATE_PARAMS          = "extension-update-params";

const XMLURI_BLOCKLIST                = "http://www.mozilla.org/2006/addons-blocklist";

const KEY_PROFILEDIR                  = "ProfD";
const KEY_APPDIR                      = "XCurProcD";
const FILE_BLOCKLIST                  = "blocklist.xml";

const BRANCH_REGEXP                   = /^([^\.]+\.[0-9]+[a-z]*).*/gi;
const PREF_EM_CHECK_COMPATIBILITY = "extensions.enableCompatibilityChecking";

const TOOLKIT_ID                      = "toolkit@mozilla.org";

const VALID_TYPES_REGEXP = /^[\w\-]+$/;

Cu.import("resource://gre/modules/Services.jsm");
Cu.import("resource://gre/modules/XPCOMUtils.jsm");
Cu.import("resource://gre/modules/AsyncShutdown.jsm");

XPCOMUtils.defineLazyModuleGetter(this, "Task",
                                  "resource://gre/modules/Task.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Promise",
                                  "resource://gre/modules/Promise.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "AddonRepository",
                                  "resource://gre/modules/addons/AddonRepository.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
                                  "resource://gre/modules/FileUtils.jsm");

XPCOMUtils.defineLazyGetter(this, "CertUtils", function certUtilsLazyGetter() {
  let certUtils = {};
  Components.utils.import("resource://gre/modules/CertUtils.jsm", certUtils);
  return certUtils;
});


this.EXPORTED_SYMBOLS = [ "AddonManager", "AddonManagerPrivate" ];

const CATEGORY_PROVIDER_MODULE = "addon-provider-module";

// A list of providers to load by default
const DEFAULT_PROVIDERS = [
  "resource://gre/modules/addons/XPIProvider.jsm",
  "resource://gre/modules/LightweightThemeManager.jsm"
];

Cu.import("resource://gre/modules/Log.jsm");
// Configure a logger at the parent 'addons' level to format
// messages for all the modules under addons.*
const PARENT_LOGGER_ID = "addons";
var parentLogger = Log.repository.getLogger(PARENT_LOGGER_ID);
parentLogger.level = Log.Level.Warn;
var formatter = new Log.BasicFormatter();
// Set parent logger (and its children) to append to
// the Javascript section of the Browser Console
parentLogger.addAppender(new Log.ConsoleAppender(formatter));
// Set parent logger (and its children) to
// also append to standard out
parentLogger.addAppender(new Log.DumpAppender(formatter));

// Create a new logger (child of 'addons' logger)
// for use by the Addons Manager
const LOGGER_ID = "addons.manager";
var logger = Log.repository.getLogger(LOGGER_ID);

// Provide the ability to enable/disable logging
// messages at runtime.
// If the "extensions.logging.enabled" preference is
// missing or 'false', messages at the WARNING and higher
// severity should be logged to the JS console and standard error.
// If "extensions.logging.enabled" is set to 'true', messages
// at DEBUG and higher should go to JS console and standard error.
const PREF_LOGGING_ENABLED = "extensions.logging.enabled";
const NS_PREFBRANCH_PREFCHANGE_TOPIC_ID = "nsPref:changed";

const UNNAMED_PROVIDER = "<unnamed-provider>";
function providerName(aProvider) {
  return aProvider.name || UNNAMED_PROVIDER;
}

/**
 * Preference listener which listens for a change in the
 * "extensions.logging.enabled" preference and changes the logging level of the
 * parent 'addons' level logger accordingly.
 */
var PrefObserver = {
    init: function() {
      Services.prefs.addObserver(PREF_LOGGING_ENABLED, this, false);
      Services.obs.addObserver(this, "xpcom-shutdown", false);
      this.observe(null, NS_PREFBRANCH_PREFCHANGE_TOPIC_ID, PREF_LOGGING_ENABLED);
    },

    observe: function(aSubject, aTopic, aData) {
      if (aTopic == "xpcom-shutdown") {
        Services.prefs.removeObserver(PREF_LOGGING_ENABLED, this);
        Services.obs.removeObserver(this, "xpcom-shutdown");
      }
      else if (aTopic == NS_PREFBRANCH_PREFCHANGE_TOPIC_ID) {
        let debugLogEnabled = Services.prefs.getBoolPref(PREF_LOGGING_ENABLED, false);
        if (debugLogEnabled) {
          parentLogger.level = Log.Level.Debug;
        }
        else {
          parentLogger.level = Log.Level.Warn;
        }
      }
    }
};

PrefObserver.init();

/**
 * Calls a callback method consuming any thrown exception. Any parameters after
 * the callback parameter will be passed to the callback.
 *
 * @param  aCallback
 *         The callback method to call
 */
function safeCall(aCallback, ...aArgs) {
  try {
    aCallback.apply(null, aArgs);
  }
  catch (e) {
    logger.warn("Exception calling callback", e);
  }
}

/**
 * Report an exception thrown by a provider API method.
 */
function reportProviderError(aProvider, aMethod, aError) {
  let method = `provider ${providerName(aProvider)}.${aMethod}`;
  AddonManagerPrivate.recordException("AMI", method, aError);
  logger.error("Exception calling " + method, aError);
}

/**
 * Calls a method on a provider if it exists and consumes any thrown exception.
 * Any parameters after the aDefault parameter are passed to the provider's method.
 *
 * @param  aProvider
 *         The provider to call
 * @param  aMethod
 *         The method name to call
 * @param  aDefault
 *         A default return value if the provider does not implement the named
 *         method or throws an error.
 * @return the return value from the provider, or aDefault if the provider does not
 *         implement method or throws an error
 */
function callProvider(aProvider, aMethod, aDefault, ...aArgs) {
  if (!(aMethod in aProvider))
    return aDefault;

  try {
    return aProvider[aMethod].apply(aProvider, aArgs);
  }
  catch (e) {
    reportProviderError(aProvider, aMethod, e);
    return aDefault;
  }
}

/**
 * Calls a method on a provider if it exists and consumes any thrown exception.
 * Parameters after aMethod are passed to aProvider.aMethod().
 * The last parameter must be a callback function.
 * If the provider does not implement the method, or the method throws, calls
 * the callback with 'undefined'.
 *
 * @param  aProvider
 *         The provider to call
 * @param  aMethod
 *         The method name to call
 */
function callProviderAsync(aProvider, aMethod, ...aArgs) {
  let callback = aArgs[aArgs.length - 1];
  if (!(aMethod in aProvider)) {
    callback(undefined);
    return;
  }
  try {
    return aProvider[aMethod].apply(aProvider, aArgs);
  }
  catch (e) {
    reportProviderError(aProvider, aMethod, e);
    callback(undefined);
    return;
  }
}

/**
 * Gets the currently selected locale for display.
 * @return  the selected locale or "en-US" if none is selected
 */
function getLocale() {
  try {
    if (Services.prefs.getBoolPref(PREF_MATCH_OS_LOCALE))
      return Services.locale.getLocaleComponentForUserAgent();
  }
  catch (e) { }

  try {
    let locale = Services.prefs.getComplexValue(PREF_SELECTED_LOCALE,
                                                Ci.nsIPrefLocalizedString);
    if (locale)
      return locale;
  }
  catch (e) { }

  try {
    return Services.prefs.getCharPref(PREF_SELECTED_LOCALE);
  }
  catch (e) { }

  return "en-US";
}

/**
 * Previously the APIs for installing add-ons from webpages accepted nsIURI
 * arguments for the installing page. They now take an nsIPrincipal but for now
 * maintain backwards compatibility by converting an nsIURI to an nsIPrincipal.
 *
 * @param  aPrincipalOrURI
 *         The argument passed to the API function. Can be null, an nsIURI or
 *         an nsIPrincipal.
 * @return an nsIPrincipal.
 */
function ensurePrincipal(principalOrURI) {
  if (principalOrURI instanceof Ci.nsIPrincipal)
    return principalOrURI;

  logger.warn("Deprecated API call, please pass a non-null nsIPrincipal instead of an nsIURI");

  // Previously a null installing URI meant allowing the install regardless.
  if (!principalOrURI) {
    return Services.scriptSecurityManager.getSystemPrincipal();
  }

  if (principalOrURI instanceof Ci.nsIURI) {
    return Services.scriptSecurityManager.createCodebasePrincipal(principalOrURI, {
      inBrowser: true
    });
  }

  // Just return whatever we have, the API method will log an error about it.
  return principalOrURI;
}

/**
 * A helper class to repeatedly call a listener with each object in an array
 * optionally checking whether the object has a method in it.
 *
 * @param  aObjects
 *         The array of objects to iterate through
 * @param  aMethod
 *         An optional method name, if not null any objects without this method
 *         will not be passed to the listener
 * @param  aListener
 *         A listener implementing nextObject and noMoreObjects methods. The
 *         former will be called with the AsyncObjectCaller as the first
 *         parameter and the object as the second. noMoreObjects will be passed
 *         just the AsyncObjectCaller
 */
function AsyncObjectCaller(aObjects, aMethod, aListener) {
  this.objects = [...aObjects];
  this.method = aMethod;
  this.listener = aListener;

  this.callNext();
}

AsyncObjectCaller.prototype = {
  objects: null,
  method: null,
  listener: null,

  /**
   * Passes the next object to the listener or calls noMoreObjects if there
   * are none left.
   */
  callNext: function() {
    if (this.objects.length == 0) {
      this.listener.noMoreObjects(this);
      return;
    }

    let object = this.objects.shift();
    if (!this.method || this.method in object)
      this.listener.nextObject(this, object);
    else
      this.callNext();
  }
};

/**
 * Listens for a browser changing origin and cancels the installs that were
 * started by it.
 */
function BrowserListener(aBrowser, aInstallingPrincipal, aInstalls) {
  this.browser = aBrowser;
  this.principal = aInstallingPrincipal;
  this.installs = aInstalls;
  this.installCount = aInstalls.length;

  aBrowser.addProgressListener(this, Ci.nsIWebProgress.NOTIFY_LOCATION);
  Services.obs.addObserver(this, "message-manager-disconnect", true);

  for (let install of this.installs)
    install.addListener(this);

  this.registered = true;
}

BrowserListener.prototype = {
  browser: null,
  installs: null,
  installCount: null,
  registered: false,

  unregister: function() {
    if (!this.registered)
      return;
    this.registered = false;

    Services.obs.removeObserver(this, "message-manager-disconnect");
    // The browser may have already been detached
    if (this.browser.removeProgressListener)
      this.browser.removeProgressListener(this);

    for (let install of this.installs)
      install.removeListener(this);
    this.installs = null;
  },

  cancelInstalls: function() {
    for (let install of this.installs) {
      try {
        install.cancel();
      }
      catch (e) {
        // Some installs may have already failed or been cancelled, ignore these
      }
    }
  },

  observe: function(subject, topic, data) {
    if (subject != this.browser.messageManager)
      return;

    // The browser's message manager has closed and so the browser is
    // going away, cancel all installs
    this.cancelInstalls();
  },

  onLocationChange: function(webProgress, request, location) {
    if (this.browser.contentPrincipal && this.principal.subsumes(this.browser.contentPrincipal))
      return;

    // The browser has navigated to a new origin so cancel all installs
    this.cancelInstalls();
  },

  onDownloadCancelled: function(install) {
    // Don't need to hear more events from this install
    install.removeListener(this);

    // Once all installs have ended unregister everything
    if (--this.installCount == 0)
      this.unregister();
  },

  onDownloadFailed: function(install) {
    this.onDownloadCancelled(install);
  },

  onInstallFailed: function(install) {
    this.onDownloadCancelled(install);
  },

  onInstallEnded: function(install) {
    this.onDownloadCancelled(install);
  },

  QueryInterface: XPCOMUtils.generateQI([Ci.nsISupportsWeakReference,
                                         Ci.nsIWebProgressListener,
                                         Ci.nsIObserver])
};

/**
 * This represents an author of an add-on (e.g. creator or developer)
 *
 * @param  aName
 *         The name of the author
 * @param  aURL
 *         The URL of the author's profile page
 */
function AddonAuthor(aName, aURL) {
  this.name = aName;
  this.url = aURL;
}

AddonAuthor.prototype = {
  name: null,
  url: null,

  // Returns the author's name, defaulting to the empty string
  toString: function() {
    return this.name || "";
  }
}

/**
 * This represents an screenshot for an add-on
 *
 * @param  aURL
 *         The URL to the full version of the screenshot
 * @param  aWidth
 *         The width in pixels of the screenshot
 * @param  aHeight
 *         The height in pixels of the screenshot
 * @param  aThumbnailURL
 *         The URL to the thumbnail version of the screenshot
 * @param  aThumbnailWidth
 *         The width in pixels of the thumbnail version of the screenshot
 * @param  aThumbnailHeight
 *         The height in pixels of the thumbnail version of the screenshot
 * @param  aCaption
 *         The caption of the screenshot
 */
function AddonScreenshot(aURL, aWidth, aHeight, aThumbnailURL,
                         aThumbnailWidth, aThumbnailHeight, aCaption) {
  this.url = aURL;
  if (aWidth) this.width = aWidth;
  if (aHeight) this.height = aHeight;
  if (aThumbnailURL) this.thumbnailURL = aThumbnailURL;
  if (aThumbnailWidth) this.thumbnailWidth = aThumbnailWidth;
  if (aThumbnailHeight) this.thumbnailHeight = aThumbnailHeight;
  if (aCaption) this.caption = aCaption;
}

AddonScreenshot.prototype = {
  url: null,
  width: null,
  height: null,
  thumbnailURL: null,
  thumbnailWidth: null,
  thumbnailHeight: null,
  caption: null,

  // Returns the screenshot URL, defaulting to the empty string
  toString: function() {
    return this.url || "";
  }
}


/**
 * This represents a compatibility override for an addon.
 *
 * @param  aType
 *         Overrride type - "compatible" or "incompatible"
 * @param  aMinVersion
 *         Minimum version of the addon to match
 * @param  aMaxVersion
 *         Maximum version of the addon to match
 * @param  aAppID
 *         Application ID used to match appMinVersion and appMaxVersion
 * @param  aAppMinVersion
 *         Minimum version of the application to match
 * @param  aAppMaxVersion
 *         Maximum version of the application to match
 */
function AddonCompatibilityOverride(aType, aMinVersion, aMaxVersion, aAppID,
                                    aAppMinVersion, aAppMaxVersion) {
  this.type = aType;
  this.minVersion = aMinVersion;
  this.maxVersion = aMaxVersion;
  this.appID = aAppID;
  this.appMinVersion = aAppMinVersion;
  this.appMaxVersion = aAppMaxVersion;
}

AddonCompatibilityOverride.prototype = {
  /**
   * Type of override - "incompatible" or "compatible".
   * Only "incompatible" is supported for now.
   */
  type: null,

  /**
   * Min version of the addon to match.
   */
  minVersion: null,

  /**
   * Max version of the addon to match.
   */
  maxVersion: null,

  /**
   * Application ID to match.
   */
  appID: null,

  /**
   * Min version of the application to match.
   */
  appMinVersion: null,

  /**
   * Max version of the application to match.
   */
  appMaxVersion: null
};


/**
 * A type of add-on, used by the UI to determine how to display different types
 * of add-ons.
 *
 * @param  aID
 *         The add-on type ID
 * @param  aLocaleURI
 *         The URI of a localized properties file to get the displayable name
 *         for the type from
 * @param  aLocaleKey
 *         The key for the string in the properties file or the actual display
 *         name if aLocaleURI is null. Include %ID% to include the type ID in
 *         the key
 * @param  aViewType
 *         The optional type of view to use in the UI
 * @param  aUIPriority
 *         The priority is used by the UI to list the types in order. Lower
 *         values push the type higher in the list.
 * @param  aFlags
 *         An option set of flags that customize the display of the add-on in
 *         the UI.
 */
function AddonType(aID, aLocaleURI, aLocaleKey, aViewType, aUIPriority, aFlags) {
  if (!aID)
    throw Components.Exception("An AddonType must have an ID", Cr.NS_ERROR_INVALID_ARG);

  if (aViewType && aUIPriority === undefined)
    throw Components.Exception("An AddonType with a defined view must have a set UI priority",
                               Cr.NS_ERROR_INVALID_ARG);

  if (!aLocaleKey)
    throw Components.Exception("An AddonType must have a displayable name",
                               Cr.NS_ERROR_INVALID_ARG);

  this.id = aID;
  this.uiPriority = aUIPriority;
  this.viewType = aViewType;
  this.flags = aFlags;

  if (aLocaleURI) {
    this.__defineGetter__("name", function nameGetter() {
      delete this.name;
      let bundle = Services.strings.createBundle(aLocaleURI);
      this.name = bundle.GetStringFromName(aLocaleKey.replace("%ID%", aID));
      return this.name;
    });
  }
  else {
    this.name = aLocaleKey;
  }
}

var gStarted = false;
var gStartupComplete = false;
var gCheckCompatibility = true;
var gStrictCompatibility = true;
var gCheckUpdateSecurityDefault = true;
var gCheckUpdateSecurity = gCheckUpdateSecurityDefault;
var gUpdateEnabled = true;
var gAutoUpdateDefault = true;
var gShutdownBarrier = null;
var gRepoShutdownState = "";
var gShutdownInProgress = false;

/**
 * This is the real manager, kept here rather than in AddonManager to keep its
 * contents hidden from API users.
 */
var AddonManagerInternal = {
  managerListeners: [],
  installListeners: [],
  addonListeners: [],
  typeListeners: [],
  pendingProviders: new Set(),
  providers: new Set(),
  providerShutdowns: new Map(),
  types: {},
  startupChanges: {},
  // Store telemetry details per addon provider
  telemetryDetails: {},

  recordTimestamp: function(name, value) {
    this.TelemetryTimestamps.add(name, value);
  },

  validateBlocklist: function() {
    let appBlocklist = FileUtils.getFile(KEY_APPDIR, [FILE_BLOCKLIST]);

    // If there is no application shipped blocklist then there is nothing to do
    if (!appBlocklist.exists())
      return;

    let profileBlocklist = FileUtils.getFile(KEY_PROFILEDIR, [FILE_BLOCKLIST]);

    // If there is no blocklist in the profile then copy the application shipped
    // one there
    if (!profileBlocklist.exists()) {
      try {
        appBlocklist.copyTo(profileBlocklist.parent, FILE_BLOCKLIST);
      }
      catch (e) {
        logger.warn("Failed to copy the application shipped blocklist to the profile", e);
      }
      return;
    }

    let fileStream = Cc["@mozilla.org/network/file-input-stream;1"].
                     createInstance(Ci.nsIFileInputStream);
    try {
      let cstream = Cc["@mozilla.org/intl/converter-input-stream;1"].
                    createInstance(Ci.nsIConverterInputStream);
      fileStream.init(appBlocklist, FileUtils.MODE_RDONLY, FileUtils.PERMS_FILE, 0);
      cstream.init(fileStream, "UTF-8", 0, 0);

      let data = "";
      let str = {};
      let read = 0;
      do {
        read = cstream.readString(0xffffffff, str);
        data += str.value;
      } while (read != 0);

      let parser = Cc["@mozilla.org/xmlextras/domparser;1"].
                   createInstance(Ci.nsIDOMParser);
      var doc = parser.parseFromString(data, "text/xml");
    }
    catch (e) {
      logger.warn("Application shipped blocklist could not be loaded", e);
      return;
    }
    finally {
      try {
        fileStream.close();
      }
      catch (e) {
        logger.warn("Unable to close blocklist file stream", e);
      }
    }

    // If the namespace is incorrect then ignore the application shipped
    // blocklist
    if (doc.documentElement.namespaceURI != XMLURI_BLOCKLIST) {
      logger.warn("Application shipped blocklist has an unexpected namespace (" +
                  doc.documentElement.namespaceURI + ")");
      return;
    }

    // If there is no lastupdate information then ignore the application shipped
    // blocklist
    if (!doc.documentElement.hasAttribute("lastupdate"))
      return;

    // If the application shipped blocklist is older than the profile blocklist
    // then do nothing
    if (doc.documentElement.getAttribute("lastupdate") <=
        profileBlocklist.lastModifiedTime)
      return;

    // Otherwise copy the application shipped blocklist to the profile
    try {
      appBlocklist.copyTo(profileBlocklist.parent, FILE_BLOCKLIST);
    }
    catch (e) {
      logger.warn("Failed to copy the application shipped blocklist to the profile", e);
    }
  },

  /**
   * Start up a provider, and register its shutdown hook if it has one
   */
  _startProvider(aProvider, aAppChanged, aOldAppVersion, aOldPlatformVersion) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    logger.debug(`Starting provider: ${providerName(aProvider)}`);
    callProvider(aProvider, "startup", null, aAppChanged, aOldAppVersion, aOldPlatformVersion);
    if ('shutdown' in aProvider) {
      let name = providerName(aProvider);
      let AMProviderShutdown = () => {
        // If the provider has been unregistered, it will have been removed from
        // this.providers. If it hasn't been unregistered, then this is a normal
        // shutdown - and we move it to this.pendingProviders incase we're
        // running in a test that will start AddonManager again.
        if (this.providers.has(aProvider)) {
          this.providers.delete(aProvider);
          this.pendingProviders.add(aProvider);
        }

        return new Promise((resolve, reject) => {
            logger.debug("Calling shutdown blocker for " + name);
            resolve(aProvider.shutdown());
          })
          .catch(err => {
            logger.warn("Failure during shutdown of " + name, err);
            AddonManagerPrivate.recordException("AMI", "Async shutdown of " + name, err);
          });
      };
      logger.debug("Registering shutdown blocker for " + name);
      this.providerShutdowns.set(aProvider, AMProviderShutdown);
      AddonManager.shutdown.addBlocker(name, AMProviderShutdown);
    }

    this.pendingProviders.delete(aProvider);
    this.providers.add(aProvider);
    logger.debug(`Provider finished startup: ${providerName(aProvider)}`);
  },

  /**
   * Initializes the AddonManager, loading any known providers and initializing
   * them.
   */
  startup: function() {
    try {
      if (gStarted)
        return;

      this.recordTimestamp("AMI_startup_begin");

      // clear this for xpcshell test restarts
      for (let provider in this.telemetryDetails)
        delete this.telemetryDetails[provider];

      let appChanged = undefined;

      let oldAppVersion = null;
      try {
        oldAppVersion = Services.prefs.getCharPref(PREF_EM_LAST_APP_VERSION);
        appChanged = Services.appinfo.version != oldAppVersion;
      }
      catch (e) { }

      let oldPlatformVersion = Services.prefs.getCharPref(PREF_EM_LAST_PLATFORM_VERSION, "");

      if (appChanged !== false) {
        logger.debug("Application has been upgraded");
        Services.prefs.setCharPref(PREF_EM_LAST_APP_VERSION,
                                   Services.appinfo.version);
        Services.prefs.setCharPref(PREF_EM_LAST_PLATFORM_VERSION,
                                   Services.appinfo.platformVersion);
        Services.prefs.setIntPref(PREF_BLOCKLIST_PINGCOUNTVERSION,
                                  (appChanged === undefined ? 0 : -1));
        this.validateBlocklist();
      }

      gCheckCompatibility = Services.prefs.getBoolPref(PREF_EM_CHECK_COMPATIBILITY,
                                                       gCheckCompatibility);
      Services.prefs.addObserver(PREF_EM_CHECK_COMPATIBILITY, this, false);

      gStrictCompatibility = Services.prefs.getBoolPref(PREF_EM_STRICT_COMPATIBILITY,
                                                        gStrictCompatibility);
      Services.prefs.addObserver(PREF_EM_STRICT_COMPATIBILITY, this, false);

      let defaultBranch = Services.prefs.getDefaultBranch("");
      gCheckUpdateSecurityDefault = defaultBranch.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY,
                                                              gCheckUpdateSecurityDefault);

      gCheckUpdateSecurity = Services.prefs.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY,
                                                        gCheckUpdateSecurity);
      Services.prefs.addObserver(PREF_EM_CHECK_UPDATE_SECURITY, this, false);

      gUpdateEnabled = Services.prefs.getBoolPref(PREF_EM_UPDATE_ENABLED, gUpdateEnabled);
      Services.prefs.addObserver(PREF_EM_UPDATE_ENABLED, this, false);

      gAutoUpdateDefault = Services.prefs.getBoolPref(PREF_EM_AUTOUPDATE_DEFAULT,
                                                      gAutoUpdateDefault);
      Services.prefs.addObserver(PREF_EM_AUTOUPDATE_DEFAULT, this, false);

      let defaultProvidersEnabled = Services.prefs.getBoolPref(PREF_DEFAULT_PROVIDERS_ENABLED, true);
      AddonManagerPrivate.recordSimpleMeasure("default_providers", defaultProvidersEnabled);

      // Ensure all default providers have had a chance to register themselves
      if (defaultProvidersEnabled) {
        for (let url of DEFAULT_PROVIDERS) {
          try {
            let scope = {};
            Components.utils.import(url, scope);
            // Sanity check - make sure the provider exports a symbol that
            // has a 'startup' method
            let syms = Object.keys(scope);
            if ((syms.length < 1) ||
                (typeof scope[syms[0]].startup != "function")) {
              logger.warn("Provider " + url + " has no startup()");
              AddonManagerPrivate.recordException("AMI", "provider " + url, "no startup()");
            }
            logger.debug("Loaded provider scope for " + url + ": " + Object.keys(scope).toSource());
          }
          catch (e) {
            AddonManagerPrivate.recordException("AMI", "provider " + url + " load failed", e);
            logger.error("Exception loading default provider \"" + url + "\"", e);
          }
        };
      }

      // Load any providers registered in the category manager
      let catman = Cc["@mozilla.org/categorymanager;1"].
                   getService(Ci.nsICategoryManager);
      let entries = catman.enumerateCategory(CATEGORY_PROVIDER_MODULE);
      while (entries.hasMoreElements()) {
        let entry = entries.getNext().QueryInterface(Ci.nsISupportsCString).data;
        let url = catman.getCategoryEntry(CATEGORY_PROVIDER_MODULE, entry);

        try {
          Components.utils.import(url, {});
          logger.debug(`Loaded provider scope for ${url}`);
        }
        catch (e) {
          AddonManagerPrivate.recordException("AMI", "provider " + url + " load failed", e);
          logger.error("Exception loading provider " + entry + " from category \"" +
                url + "\"", e);
        }
      }

      // Register our shutdown handler with the AsyncShutdown manager
      gShutdownBarrier = new AsyncShutdown.Barrier("AddonManager: Waiting for providers to shut down.");
      AsyncShutdown.profileBeforeChange.addBlocker("AddonManager: shutting down.",
                                                   this.shutdownManager.bind(this),
                                                   {fetchState: this.shutdownState.bind(this)});

      // Once we start calling providers we must allow all normal methods to work.
      gStarted = true;

      for (let provider of this.pendingProviders) {
        this._startProvider(provider, appChanged, oldAppVersion, oldPlatformVersion);
      }

      // If this is a new profile just pretend that there were no changes
      if (appChanged === undefined) {
        for (let type in this.startupChanges)
          delete this.startupChanges[type];
      }

      gStartupComplete = true;
      this.recordTimestamp("AMI_startup_end");
    }
    catch (e) {
      logger.error("startup failed", e);
      AddonManagerPrivate.recordException("AMI", "startup failed", e);
    }

    logger.debug("Completed startup sequence");
    this.callManagerListeners("onStartup");
  },

  /**
   * Registers a new AddonProvider.
   *
   * @param  aProvider
   *         The provider to register
   * @param  aTypes
   *         An optional array of add-on types
   */
  registerProvider: function(aProvider, aTypes) {
    if (!aProvider || typeof aProvider != "object")
      throw Components.Exception("aProvider must be specified",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aTypes && !Array.isArray(aTypes))
      throw Components.Exception("aTypes must be an array or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    this.pendingProviders.add(aProvider);

    if (aTypes) {
      aTypes.forEach(function(aType) {
        if (!(aType.id in this.types)) {
          if (!VALID_TYPES_REGEXP.test(aType.id)) {
            logger.warn("Ignoring invalid type " + aType.id);
            return;
          }

          this.types[aType.id] = {
            type: aType,
            providers: [aProvider]
          };

          let typeListeners = this.typeListeners.slice(0);
          for (let listener of typeListeners) {
            safeCall(function listenerSafeCall() {
              listener.onTypeAdded(aType);
            });
          }
        }
        else {
          this.types[aType.id].providers.push(aProvider);
        }
      }, this);
    }

    // If we're registering after startup call this provider's startup.
    if (gStarted) {
      this._startProvider(aProvider);
    }
  },

  /**
   * Unregisters an AddonProvider.
   *
   * @param  aProvider
   *         The provider to unregister
   * @return Whatever the provider's 'shutdown' method returns (if anything).
   *         For providers that have async shutdown methods returning Promises,
   *         the caller should wait for that Promise to resolve.
   */
  unregisterProvider: function(aProvider) {
    if (!aProvider || typeof aProvider != "object")
      throw Components.Exception("aProvider must be specified",
                                 Cr.NS_ERROR_INVALID_ARG);

    this.providers.delete(aProvider);
    // The test harness will unregister XPIProvider *after* shutdown, which is
    // after the provider will have been moved from providers to
    // pendingProviders.
    this.pendingProviders.delete(aProvider);

    for (let type in this.types) {
      this.types[type].providers = this.types[type].providers.filter(function filterProvider(p) p != aProvider);
      if (this.types[type].providers.length == 0) {
        let oldType = this.types[type].type;
        delete this.types[type];

        let typeListeners = this.typeListeners.slice(0);
        for (let listener of typeListeners) {
          safeCall(function listenerSafeCall() {
            listener.onTypeRemoved(oldType);
          });
        }
      }
    }

    // If we're unregistering after startup but before shutting down,
    // remove the blocker for this provider's shutdown and call it.
    // If we're already shutting down, just let gShutdownBarrier call it to avoid races.
    if (gStarted && !gShutdownInProgress) {
      logger.debug("Unregistering shutdown blocker for " + providerName(aProvider));
      let shutter = this.providerShutdowns.get(aProvider);
      if (shutter) {
        this.providerShutdowns.delete(aProvider);
        gShutdownBarrier.client.removeBlocker(shutter);
        return shutter();
      }
    }
    return undefined;
  },

  /**
   * Mark a provider as safe to access via AddonManager APIs, before its
   * startup has completed.
   *
   * Normally a provider isn't marked as safe until after its (synchronous)
   * startup() method has returned. Until a provider has been marked safe,
   * it won't be used by any of the AddonManager APIs. markProviderSafe()
   * allows a provider to mark itself as safe during its startup; this can be
   * useful if the provider wants to perform tasks that block startup, which
   * happen after its required initialization tasks and therefore when the
   * provider is in a safe state.
   *
   * @param aProvider Provider object to mark safe
   */
  markProviderSafe: function(aProvider) {
    if (!gStarted) {
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);
    }

    if (!aProvider || typeof aProvider != "object") {
      throw Components.Exception("aProvider must be specified",
                                 Cr.NS_ERROR_INVALID_ARG);
    }

    if (!this.pendingProviders.has(aProvider)) {
      return;
    }

    this.pendingProviders.delete(aProvider);
    this.providers.add(aProvider);
  },

  /**
   * Calls a method on all registered providers if it exists and consumes any
   * thrown exception. Return values are ignored. Any parameters after the
   * method parameter are passed to the provider's method.
   * WARNING: Do not use for asynchronous calls; callProviders() does not
   * invoke callbacks if provider methods throw synchronous exceptions.
   *
   * @param  aMethod
   *         The method name to call
   * @see    callProvider
   */
  callProviders: function(aMethod, ...aArgs) {
    if (!aMethod || typeof aMethod != "string")
      throw Components.Exception("aMethod must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    let providers = [...this.providers];
    for (let provider of providers) {
      try {
        if (aMethod in provider)
          provider[aMethod].apply(provider, aArgs);
      }
      catch (e) {
        reportProviderError(aProvider, aMethod, e);
      }
    }
  },

  /**
   * Report the current state of asynchronous shutdown
   */
  shutdownState() {
    let state = [];
    if (gShutdownBarrier) {
      state.push({
        name: gShutdownBarrier.client.name,
        state: gShutdownBarrier.state
      });
    }
    state.push({
      name: "AddonRepository: async shutdown",
      state: gRepoShutdownState
    });
    return state;
  },

  /**
   * Shuts down the addon manager and all registered providers, this must clean
   * up everything in order for automated tests to fake restarts.
   * @return Promise{null} that resolves when all providers and dependent modules
   *                       have finished shutting down
   */
  shutdownManager: Task.async(function* () {
    logger.debug("shutdown");
    this.callManagerListeners("onShutdown");

    gRepoShutdownState = "pending";
    gShutdownInProgress = true;
    // Clean up listeners
    Services.prefs.removeObserver(PREF_EM_CHECK_COMPATIBILITY, this);
    Services.prefs.removeObserver(PREF_EM_STRICT_COMPATIBILITY, this);
    Services.prefs.removeObserver(PREF_EM_CHECK_UPDATE_SECURITY, this);
    Services.prefs.removeObserver(PREF_EM_UPDATE_ENABLED, this);
    Services.prefs.removeObserver(PREF_EM_AUTOUPDATE_DEFAULT, this);

    let savedError = null;
    // Only shut down providers if they've been started.
    if (gStarted) {
      try {
        yield gShutdownBarrier.wait();
      }
      catch(err) {
        savedError = err;
        logger.error("Failure during wait for shutdown barrier", err);
        AddonManagerPrivate.recordException("AMI", "Async shutdown of AddonManager providers", err);
      }
    }

    // Shut down AddonRepository after providers (if any).
    try {
      gRepoShutdownState = "in progress";
      yield AddonRepository.shutdown();
      gRepoShutdownState = "done";
    }
    catch(err) {
      savedError = err;
      logger.error("Failure during AddonRepository shutdown", err);
      AddonManagerPrivate.recordException("AMI", "Async shutdown of AddonRepository", err);
    }

    logger.debug("Async provider shutdown done");
    this.managerListeners.splice(0, this.managerListeners.length);
    this.installListeners.splice(0, this.installListeners.length);
    this.addonListeners.splice(0, this.addonListeners.length);
    this.typeListeners.splice(0, this.typeListeners.length);
    this.providerShutdowns.clear();
    for (let type in this.startupChanges)
      delete this.startupChanges[type];
    gStarted = false;
    gStartupComplete = false;
    gShutdownBarrier = null;
    gShutdownInProgress = false;
    if (savedError) {
      throw savedError;
    }
  }),

  /**
   * Notified when a preference we're interested in has changed.
   *
   * @see nsIObserver
   */
  observe: function(aSubject, aTopic, aData) {
    switch (aData) {
      case PREF_EM_CHECK_COMPATIBILITY: {
        let oldValue = gCheckCompatibility;
        gCheckCompatibility = Services.prefs.getBoolPref(PREF_EM_CHECK_COMPATIBILITY, true);

        this.callManagerListeners("onCompatibilityModeChanged");

        if (gCheckCompatibility != oldValue)
          this.updateAddonAppDisabledStates();

        break;
      }
      case PREF_EM_STRICT_COMPATIBILITY: {
        let oldValue = gStrictCompatibility;
        gStrictCompatibility = Services.prefs.getBoolPref(PREF_EM_STRICT_COMPATIBILITY, true);

        this.callManagerListeners("onCompatibilityModeChanged");

        if (gStrictCompatibility != oldValue)
          this.updateAddonAppDisabledStates();

        break;
      }
      case PREF_EM_CHECK_UPDATE_SECURITY: {
        let oldValue = gCheckUpdateSecurity;
        gCheckUpdateSecurity = Services.prefs.getBoolPref(PREF_EM_CHECK_UPDATE_SECURITY, true);

        this.callManagerListeners("onCheckUpdateSecurityChanged");

        if (gCheckUpdateSecurity != oldValue)
          this.updateAddonAppDisabledStates();

        break;
      }
      case PREF_EM_UPDATE_ENABLED: {
        let oldValue = gUpdateEnabled;
        gUpdateEnabled = Services.prefs.getBoolPref(PREF_EM_UPDATE_ENABLED, true);

        this.callManagerListeners("onUpdateModeChanged");
        break;
      }
      case PREF_EM_AUTOUPDATE_DEFAULT: {
        let oldValue = gAutoUpdateDefault;
        gAutoUpdateDefault = Services.prefs.getBoolPref(PREF_EM_AUTOUPDATE_DEFAULT, true);

        this.callManagerListeners("onUpdateModeChanged");
        break;
      }
    }
  },

  /**
   * Replaces %...% strings in an addon url (update and updateInfo) with
   * appropriate values.
   *
   * @param  aAddon
   *         The Addon representing the add-on
   * @param  aUri
   *         The string representation of the URI to escape
   * @param  aAppVersion
   *         The optional application version to use for %APP_VERSION%
   * @return The appropriately escaped URI.
   */
  escapeAddonURI: function(aAddon, aUri, aAppVersion)
  {
    if (!aAddon || typeof aAddon != "object")
      throw Components.Exception("aAddon must be an Addon object",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!aUri || typeof aUri != "string")
      throw Components.Exception("aUri must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aAppVersion && typeof aAppVersion != "string")
      throw Components.Exception("aAppVersion must be a string or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    var addonStatus = aAddon.userDisabled || aAddon.softDisabled ? "userDisabled"
                                                                 : "userEnabled";

    if (!aAddon.isCompatible)
      addonStatus += ",incompatible";
    if (aAddon.blocklistState == Ci.nsIBlocklistService.STATE_BLOCKED)
      addonStatus += ",blocklisted";
    if (aAddon.blocklistState == Ci.nsIBlocklistService.STATE_SOFTBLOCKED)
      addonStatus += ",softblocked";

    try {
      var xpcomABI = Services.appinfo.XPCOMABI;
    } catch (ex) {
      xpcomABI = UNKNOWN_XPCOM_ABI;
    }

    let uri = aUri.replace(/%ITEM_ID%/g, aAddon.id);
    uri = uri.replace(/%ITEM_VERSION%/g, aAddon.version);
    uri = uri.replace(/%ITEM_STATUS%/g, addonStatus);
    uri = uri.replace(/%APP_ID%/g, Services.appinfo.ID);
    uri = uri.replace(/%APP_VERSION%/g, aAppVersion ? aAppVersion :
                                                      Services.appinfo.version);
    uri = uri.replace(/%REQ_VERSION%/g, UPDATE_REQUEST_VERSION);
    uri = uri.replace(/%APP_OS%/g, Services.appinfo.OS);
    uri = uri.replace(/%APP_ABI%/g, xpcomABI);
    uri = uri.replace(/%APP_LOCALE%/g, getLocale());
    uri = uri.replace(/%CURRENT_APP_VERSION%/g, Services.appinfo.version);

    // Replace custom parameters (names of custom parameters must have at
    // least 3 characters to prevent lookups for something like %D0%C8)
    var catMan = null;
    uri = uri.replace(/%(\w{3,})%/g, function parameterReplace(aMatch, aParam) {
      if (!catMan) {
        catMan = Cc["@mozilla.org/categorymanager;1"].
                 getService(Ci.nsICategoryManager);
      }

      try {
        var contractID = catMan.getCategoryEntry(CATEGORY_UPDATE_PARAMS, aParam);
        var paramHandler = Cc[contractID].getService(Ci.nsIPropertyBag2);
        return paramHandler.getPropertyAsAString(aParam);
      }
      catch(e) {
        return aMatch;
      }
    });

    // escape() does not properly encode + symbols in any embedded FVF strings.
    return uri.replace(/\+/g, "%2B");
  },

  /**
   * Performs a background update check by starting an update for all add-ons
   * that can be updated.
   * @return Promise{null} Resolves when the background update check is complete
   *                       (the resulting addon installations may still be in progress).
   */
  backgroundUpdateCheck: function() {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    let buPromise = Task.spawn(function* backgroundUpdateTask() {
      logger.debug("Background update check beginning");

      Services.obs.notifyObservers(null, "addons-background-update-start", null);

      if (this.updateEnabled) {
        let scope = {};
        Components.utils.import("resource://gre/modules/LightweightThemeManager.jsm", scope);
        scope.LightweightThemeManager.updateCurrentTheme();

        let allAddons = yield new Promise((resolve, reject) => this.getAllAddons(resolve));

        // Repopulate repository cache first, to ensure compatibility overrides
        // are up to date before checking for addon updates.
        yield AddonRepository.backgroundUpdateCheck();

        // Keep track of all the async add-on updates happening in parallel
        let updates = [];

        for (let addon of allAddons) {
          // Check all add-ons for updates so that any compatibility updates will
          // be applied
          updates.push(new Promise((resolve, reject) => {
            addon.findUpdates({
              onUpdateAvailable: function(aAddon, aInstall) {
                // Start installing updates when the add-on can be updated and
                // background updates should be applied.
                logger.debug("Found update for add-on ${id}", aAddon);
                if (aAddon.permissions & AddonManager.PERM_CAN_UPGRADE &&
                    AddonManager.shouldAutoUpdate(aAddon)) {
                  // XXX we really should resolve when this install is done,
                  // not when update-available check completes, no?
                  logger.debug("Starting install of ${id}", aAddon);
                  aInstall.install();
                }
              },

              onUpdateFinished: aAddon => { logger.debug("onUpdateFinished for ${id}", aAddon); resolve(); }
            }, AddonManager.UPDATE_WHEN_PERIODIC_UPDATE);
          }));
        }
        yield Promise.all(updates);
      }

      logger.debug("Background update check complete");
      Services.obs.notifyObservers(null,
                                   "addons-background-update-complete",
                                   null);
    }.bind(this));
    // Fork the promise chain so we can log the error and let our caller see it too.
    buPromise.then(null, e => logger.warn("Error in background update", e));
    return buPromise;
  },

  /**
   * Adds a add-on to the list of detected changes for this startup. If
   * addStartupChange is called multiple times for the same add-on in the same
   * startup then only the most recent change will be remembered.
   *
   * @param  aType
   *         The type of change as a string. Providers can define their own
   *         types of changes or use the existing defined STARTUP_CHANGE_*
   *         constants
   * @param  aID
   *         The ID of the add-on
   */
  addStartupChange: function(aType, aID) {
    if (!aType || typeof aType != "string")
      throw Components.Exception("aType must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!aID || typeof aID != "string")
      throw Components.Exception("aID must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (gStartupComplete)
      return;

    // Ensure that an ID is only listed in one type of change
    for (let type in this.startupChanges)
      this.removeStartupChange(type, aID);

    if (!(aType in this.startupChanges))
      this.startupChanges[aType] = [];
    this.startupChanges[aType].push(aID);
  },

  /**
   * Removes a startup change for an add-on.
   *
   * @param  aType
   *         The type of change
   * @param  aID
   *         The ID of the add-on
   */
  removeStartupChange: function(aType, aID) {
    if (!aType || typeof aType != "string")
      throw Components.Exception("aType must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!aID || typeof aID != "string")
      throw Components.Exception("aID must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (gStartupComplete)
      return;

    if (!(aType in this.startupChanges))
      return;

    this.startupChanges[aType] = this.startupChanges[aType].filter(
                                 function filterItem(aItem) aItem != aID);
  },

  /**
   * Calls all registered AddonManagerListeners with an event. Any parameters
   * after the method parameter are passed to the listener.
   *
   * @param  aMethod
   *         The method on the listeners to call
   */
  callManagerListeners: function(aMethod, ...aArgs) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aMethod || typeof aMethod != "string")
      throw Components.Exception("aMethod must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    let managerListeners = this.managerListeners.slice(0);
    for (let listener of managerListeners) {
      try {
        if (aMethod in listener)
          listener[aMethod].apply(listener, aArgs);
      }
      catch (e) {
        logger.warn("AddonManagerListener threw exception when calling " + aMethod, e);
      }
    }
  },

  /**
   * Calls all registered InstallListeners with an event. Any parameters after
   * the extraListeners parameter are passed to the listener.
   *
   * @param  aMethod
   *         The method on the listeners to call
   * @param  aExtraListeners
   *         An optional array of extra InstallListeners to also call
   * @return false if any of the listeners returned false, true otherwise
   */
  callInstallListeners: function(aMethod,
                                 aExtraListeners, ...aArgs) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aMethod || typeof aMethod != "string")
      throw Components.Exception("aMethod must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aExtraListeners && !Array.isArray(aExtraListeners))
      throw Components.Exception("aExtraListeners must be an array or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    let result = true;
    let listeners;
    if (aExtraListeners)
      listeners = aExtraListeners.concat(this.installListeners);
    else
      listeners = this.installListeners.slice(0);

    for (let listener of listeners) {
      try {
        if (aMethod in listener) {
          if (listener[aMethod].apply(listener, aArgs) === false)
            result = false;
        }
      }
      catch (e) {
        logger.warn("InstallListener threw exception when calling " + aMethod, e);
      }
    }
    return result;
  },

  /**
   * Calls all registered AddonListeners with an event. Any parameters after
   * the method parameter are passed to the listener.
   *
   * @param  aMethod
   *         The method on the listeners to call
   */
  callAddonListeners: function(aMethod, ...aArgs) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aMethod || typeof aMethod != "string")
      throw Components.Exception("aMethod must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    let addonListeners = this.addonListeners.slice(0);
    for (let listener of addonListeners) {
      try {
        if (aMethod in listener)
          listener[aMethod].apply(listener, aArgs);
      }
      catch (e) {
        logger.warn("AddonListener threw exception when calling " + aMethod, e);
      }
    }
  },

  /**
   * Notifies all providers that an add-on has been enabled when that type of
   * add-on only supports a single add-on being enabled at a time. This allows
   * the providers to disable theirs if necessary.
   *
   * @param  aID
   *         The ID of the enabled add-on
   * @param  aType
   *         The type of the enabled add-on
   * @param  aPendingRestart
   *         A boolean indicating if the change will only take place the next
   *         time the application is restarted
   */
  notifyAddonChanged: function(aID, aType, aPendingRestart) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (aID && typeof aID != "string")
      throw Components.Exception("aID must be a string or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!aType || typeof aType != "string")
      throw Components.Exception("aType must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    // Temporary hack until bug 520124 lands.
    // We can get here during synchronous startup, at which point it's
    // considered unsafe (and therefore disallowed by AddonManager.jsm) to
    // access providers that haven't been initialized yet. Since this is when
    // XPIProvider is starting up, XPIProvider can't access itself via APIs
    // going through AddonManager.jsm. Furthermore, LightweightThemeManager may
    // not be initialized until after XPIProvider is, and therefore would also
    // be unaccessible during XPIProvider startup. Thankfully, these are the
    // only two uses of this API, and we know it's safe to use this API with
    // both providers; so we have this hack to allow bypassing the normal
    // safetey guard.
    // The notifyAddonChanged/addonChanged API will be unneeded and therefore
    // removed by bug 520124, so this is a temporary quick'n'dirty hack.
    let providers = [...this.providers, ...this.pendingProviders];
    for (let provider of providers) {
      callProvider(provider, "addonChanged", null, aID, aType, aPendingRestart);
    }
  },

  /**
   * Notifies all providers they need to update the appDisabled property for
   * their add-ons in response to an application change such as a blocklist
   * update.
   */
  updateAddonAppDisabledStates: function() {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    this.callProviders("updateAddonAppDisabledStates");
  },

  /**
   * Notifies all providers that the repository has updated its data for
   * installed add-ons.
   *
   * @param  aCallback
   *         Function to call when operation is complete.
   */
  updateAddonRepositoryData: function(aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    new AsyncObjectCaller(this.providers, "updateAddonRepositoryData", {
      nextObject: function(aCaller, aProvider) {
        callProviderAsync(aProvider, "updateAddonRepositoryData",
                          aCaller.callNext.bind(aCaller));
      },
      noMoreObjects: function(aCaller) {
        safeCall(aCallback);
        // only tests should care about this
        Services.obs.notifyObservers(null, "TEST:addon-repository-data-updated", null);
      }
    });
  },

  /**
   * Asynchronously gets an AddonInstall for a URL.
   *
   * @param  aUrl
   *         The string represenation of the URL the add-on is located at
   * @param  aCallback
   *         A callback to pass the AddonInstall to
   * @param  aMimetype
   *         The mimetype of the add-on
   * @param  aHash
   *         An optional hash of the add-on
   * @param  aName
   *         An optional placeholder name while the add-on is being downloaded
   * @param  aIcons
   *         Optional placeholder icons while the add-on is being downloaded
   * @param  aVersion
   *         An optional placeholder version while the add-on is being downloaded
   * @param  aLoadGroup
   *         An optional nsILoadGroup to associate any network requests with
   * @throws if the aUrl, aCallback or aMimetype arguments are not specified
   */
  getInstallForURL: function(aUrl, aCallback, aMimetype,
                                                  aHash, aName, aIcons,
                                                  aVersion, aBrowser) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aUrl || typeof aUrl != "string")
      throw Components.Exception("aURL must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!aMimetype || typeof aMimetype != "string")
      throw Components.Exception("aMimetype must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aHash && typeof aHash != "string")
      throw Components.Exception("aHash must be a string or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aName && typeof aName != "string")
      throw Components.Exception("aName must be a string or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aIcons) {
      if (typeof aIcons == "string")
        aIcons = { "32": aIcons };
      else if (typeof aIcons != "object")
        throw Components.Exception("aIcons must be a string, an object or null",
                                   Cr.NS_ERROR_INVALID_ARG);
    } else {
      aIcons = {};
    }

    if (aVersion && typeof aVersion != "string")
      throw Components.Exception("aVersion must be a string or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aBrowser && (!(aBrowser instanceof Ci.nsIDOMElement)))
      throw Components.Exception("aBrowser must be a nsIDOMElement or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    let providers = [...this.providers];
    for (let provider of providers) {
      if (callProvider(provider, "supportsMimetype", false, aMimetype)) {
        callProviderAsync(provider, "getInstallForURL",
                          aUrl, aHash, aName, aIcons, aVersion, aBrowser,
                          function  getInstallForURL_safeCall(aInstall) {
          safeCall(aCallback, aInstall);
        });
        return;
      }
    }
    safeCall(aCallback, null);
  },

  /**
   * Asynchronously gets an AddonInstall for an nsIFile.
   *
   * @param  aFile
   *         The nsIFile where the add-on is located
   * @param  aCallback
   *         A callback to pass the AddonInstall to
   * @param  aMimetype
   *         An optional mimetype hint for the add-on
   * @throws if the aFile or aCallback arguments are not specified
   */
  getInstallForFile: function(aFile, aCallback, aMimetype) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!(aFile instanceof Ci.nsIFile))
      throw Components.Exception("aFile must be a nsIFile",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aMimetype && typeof aMimetype != "string")
      throw Components.Exception("aMimetype must be a string or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    new AsyncObjectCaller(this.providers, "getInstallForFile", {
      nextObject: function(aCaller, aProvider) {
        callProviderAsync(aProvider, "getInstallForFile", aFile,
                          function getInstallForFile_safeCall(aInstall) {
          if (aInstall)
            safeCall(aCallback, aInstall);
          else
            aCaller.callNext();
        });
      },

      noMoreObjects: function(aCaller) {
        safeCall(aCallback, null);
      }
    });
  },

  /**
   * Asynchronously gets all current AddonInstalls optionally limiting to a list
   * of types.
   *
   * @param  aTypes
   *         An optional array of types to retrieve. Each type is a string name
   * @param  aCallback
   *         A callback which will be passed an array of AddonInstalls
   * @throws If the aCallback argument is not specified
   */
  getInstallsByTypes: function(aTypes, aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (aTypes && !Array.isArray(aTypes))
      throw Components.Exception("aTypes must be an array or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    let installs = [];

    new AsyncObjectCaller(this.providers, "getInstallsByTypes", {
      nextObject: function(aCaller, aProvider) {
        callProviderAsync(aProvider, "getInstallsByTypes", aTypes,
                          function getInstallsByTypes_safeCall(aProviderInstalls) {
          if (aProviderInstalls) {
            installs = installs.concat(aProviderInstalls);
          }
          aCaller.callNext();
        });
      },

      noMoreObjects: function(aCaller) {
        safeCall(aCallback, installs);
      }
    });
  },

  /**
   * Asynchronously gets all current AddonInstalls.
   *
   * @param  aCallback
   *         A callback which will be passed an array of AddonInstalls
   */
  getAllInstalls: function(aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    this.getInstallsByTypes(null, aCallback);
  },

  /**
   * Synchronously map a URI to the corresponding Addon ID.
   *
   * Mappable URIs are limited to in-application resources belonging to the
   * add-on, such as Javascript compartments, XUL windows, XBL bindings, etc.
   * but do not include URIs from meta data, such as the add-on homepage.
   *
   * @param  aURI
   *         nsIURI to map to an addon id
   * @return string containing the Addon ID or null
   * @see    amIAddonManager.mapURIToAddonID
   */
  mapURIToAddonID: function(aURI) {
    if (!(aURI instanceof Ci.nsIURI)) {
      throw Components.Exception("aURI is not a nsIURI",
                                 Cr.NS_ERROR_INVALID_ARG);
    }

    // Try all providers
    let providers = [...this.providers];
    for (let provider of providers) {
      var id = callProvider(provider, "mapURIToAddonID", null, aURI);
      if (id !== null) {
        return id;
      }
    }

    return null;
  },

  /**
   * Checks whether installation is enabled for a particular mimetype.
   *
   * @param  aMimetype
   *         The mimetype to check
   * @return true if installation is enabled for the mimetype
   */
  isInstallEnabled: function(aMimetype) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aMimetype || typeof aMimetype != "string")
      throw Components.Exception("aMimetype must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    let providers = [...this.providers];
    for (let provider of providers) {
      if (callProvider(provider, "supportsMimetype", false, aMimetype) &&
          callProvider(provider, "isInstallEnabled"))
        return true;
    }
    return false;
  },

  /**
   * Checks whether a particular source is allowed to install add-ons of a
   * given mimetype.
   *
   * @param  aMimetype
   *         The mimetype of the add-on
   * @param  aInstallingPrincipal
   *         The nsIPrincipal that initiated the install
   * @return true if the source is allowed to install this mimetype
   */
  isInstallAllowed: function(aMimetype, aInstallingPrincipal) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aMimetype || typeof aMimetype != "string")
      throw Components.Exception("aMimetype must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!aInstallingPrincipal || !(aInstallingPrincipal instanceof Ci.nsIPrincipal))
      throw Components.Exception("aInstallingPrincipal must be a nsIPrincipal",
                                 Cr.NS_ERROR_INVALID_ARG);

    let providers = [...this.providers];
    for (let provider of providers) {
      if (callProvider(provider, "supportsMimetype", false, aMimetype) &&
          callProvider(provider, "isInstallAllowed", null, aInstallingPrincipal))
        return true;
    }
    return false;
  },

  /**
   * Starts installation of an array of AddonInstalls notifying the registered
   * web install listener of blocked or started installs.
   *
   * @param  aMimetype
   *         The mimetype of add-ons being installed
   * @param  aBrowser
   *         The optional browser element that started the installs
   * @param  aInstallingPrincipal
   *         The nsIPrincipal that initiated the install
   * @param  aInstalls
   *         The array of AddonInstalls to be installed
   */
  installAddonsFromWebpage: function(aMimetype, aBrowser, aInstallingPrincipal, aInstalls) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aMimetype || typeof aMimetype != "string")
      throw Components.Exception("aMimetype must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (aBrowser && !(aBrowser instanceof Ci.nsIDOMElement))
      throw Components.Exception("aSource must be a nsIDOMElement, or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!aInstallingPrincipal || !(aInstallingPrincipal instanceof Ci.nsIPrincipal))
      throw Components.Exception("aInstallingPrincipal must be a nsIPrincipal",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!Array.isArray(aInstalls))
      throw Components.Exception("aInstalls must be an array",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!("@mozilla.org/addons/web-install-listener;1" in Cc)) {
      logger.warn("No web installer available, cancelling all installs");
      aInstalls.forEach(function(aInstall) {
        aInstall.cancel();
      });
      return;
    }

    // When a chrome in-content UI has loaded a <browser> inside to host a
    // website we want to do our security checks on the inner-browser but
    // notify front-end that install events came from the outer-browser (the
    // main tab's browser). Check this by seeing if the browser we've been
    // passed is in a content type docshell and if so get the outer-browser.
    let topBrowser = aBrowser;
    let docShell = aBrowser.ownerDocument.defaultView
                           .QueryInterface(Ci.nsIInterfaceRequestor)
                           .getInterface(Ci.nsIDocShell)
                           .QueryInterface(Ci.nsIDocShellTreeItem);
    if (docShell.itemType == Ci.nsIDocShellTreeItem.typeContent)
      topBrowser = docShell.chromeEventHandler;

    try {
      let weblistener = Cc["@mozilla.org/addons/web-install-listener;1"].
                        getService(Ci.amIWebInstallListener);

      if (!this.isInstallEnabled(aMimetype)) {
        for (let install of aInstalls)
          install.cancel();

        weblistener.onWebInstallDisabled(topBrowser, aInstallingPrincipal.URI,
                                         aInstalls, aInstalls.length);
        return;
      }
      else if (!aBrowser.contentPrincipal || !aInstallingPrincipal.subsumes(aBrowser.contentPrincipal)) {
        for (let install of aInstalls)
          install.cancel();

        if (weblistener instanceof Ci.amIWebInstallListener2) {
          weblistener.onWebInstallOriginBlocked(topBrowser, aInstallingPrincipal.URI,
                                                aInstalls, aInstalls.length);
        }
        return;
      }

      // The installs may start now depending on the web install listener,
      // listen for the browser navigating to a new origin and cancel the
      // installs in that case.
      new BrowserListener(aBrowser, aInstallingPrincipal, aInstalls);

      if (!this.isInstallAllowed(aMimetype, aInstallingPrincipal)) {
        if (weblistener.onWebInstallBlocked(topBrowser, aInstallingPrincipal.URI,
                                            aInstalls, aInstalls.length)) {
          aInstalls.forEach(function(aInstall) {
            aInstall.install();
          });
        }
      }
      else if (weblistener.onWebInstallRequested(topBrowser, aInstallingPrincipal.URI,
                                                 aInstalls, aInstalls.length)) {
        aInstalls.forEach(function(aInstall) {
          aInstall.install();
        });
      }
    }
    catch (e) {
      // In the event that the weblistener throws during instantiation or when
      // calling onWebInstallBlocked or onWebInstallRequested all of the
      // installs should get cancelled.
      logger.warn("Failure calling web installer", e);
      aInstalls.forEach(function(aInstall) {
        aInstall.cancel();
      });
    }
  },

  /**
   * Adds a new InstallListener if the listener is not already registered.
   *
   * @param  aListener
   *         The InstallListener to add
   */
  addInstallListener: function(aListener) {
    if (!aListener || typeof aListener != "object")
      throw Components.Exception("aListener must be a InstallListener object",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!this.installListeners.some(function addInstallListener_matchListener(i) {
      return i == aListener; }))
      this.installListeners.push(aListener);
  },

  /**
   * Removes an InstallListener if the listener is registered.
   *
   * @param  aListener
   *         The InstallListener to remove
   */
  removeInstallListener: function(aListener) {
    if (!aListener || typeof aListener != "object")
      throw Components.Exception("aListener must be a InstallListener object",
                                 Cr.NS_ERROR_INVALID_ARG);

    let pos = 0;
    while (pos < this.installListeners.length) {
      if (this.installListeners[pos] == aListener)
        this.installListeners.splice(pos, 1);
      else
        pos++;
    }
  },

  /**
   * Asynchronously gets an add-on with a specific ID.
   *
   * @param  aID
   *         The ID of the add-on to retrieve
   * @param  aCallback
   *         The callback to pass the retrieved add-on to
   * @throws if the aID or aCallback arguments are not specified
   */
  getAddonByID: function(aID, aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aID || typeof aID != "string")
      throw Components.Exception("aID must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    new AsyncObjectCaller(this.providers, "getAddonByID", {
      nextObject: function(aCaller, aProvider) {
        callProviderAsync(aProvider, "getAddonByID", aID,
                          function getAddonByID_safeCall(aAddon) {
          if (aAddon)
            safeCall(aCallback, aAddon);
          else
            aCaller.callNext();
        });
      },

      noMoreObjects: function(aCaller) {
        safeCall(aCallback, null);
      }
    });
  },

  /**
   * Asynchronously get an add-on with a specific Sync GUID.
   *
   * @param  aGUID
   *         String GUID of add-on to retrieve
   * @param  aCallback
   *         The callback to pass the retrieved add-on to.
   * @throws if the aGUID or aCallback arguments are not specified
   */
  getAddonBySyncGUID: function(aGUID, aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!aGUID || typeof aGUID != "string")
      throw Components.Exception("aGUID must be a non-empty string",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    new AsyncObjectCaller(this.providers, "getAddonBySyncGUID", {
      nextObject: function(aCaller, aProvider) {
        callProviderAsync(aProvider, "getAddonBySyncGUID", aGUID,
                          function getAddonBySyncGUID_safeCall(aAddon) {
          if (aAddon) {
            safeCall(aCallback, aAddon);
          } else {
            aCaller.callNext();
          }
        });
      },

      noMoreObjects: function(aCaller) {
        safeCall(aCallback, null);
      }
    });
  },

  /**
   * Asynchronously gets an array of add-ons.
   *
   * @param  aIDs
   *         The array of IDs to retrieve
   * @param  aCallback
   *         The callback to pass an array of Addons to
   * @throws if the aID or aCallback arguments are not specified
   */
  getAddonsByIDs: function(aIDs, aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (!Array.isArray(aIDs))
      throw Components.Exception("aIDs must be an array",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    let addons = [];

    new AsyncObjectCaller(aIDs, null, {
      nextObject: function(aCaller, aID) {
        AddonManagerInternal.getAddonByID(aID,
                             function getAddonsByIDs_getAddonByID(aAddon) {
          addons.push(aAddon);
          aCaller.callNext();
        });
      },

      noMoreObjects: function(aCaller) {
        safeCall(aCallback, addons);
      }
    });
  },

  /**
   * Asynchronously gets add-ons of specific types.
   *
   * @param  aTypes
   *         An optional array of types to retrieve. Each type is a string name
   * @param  aCallback
   *         The callback to pass an array of Addons to.
   * @throws if the aCallback argument is not specified
   */
  getAddonsByTypes: function(aTypes, aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (aTypes && !Array.isArray(aTypes))
      throw Components.Exception("aTypes must be an array or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    let addons = [];

    new AsyncObjectCaller(this.providers, "getAddonsByTypes", {
      nextObject: function(aCaller, aProvider) {
        callProviderAsync(aProvider, "getAddonsByTypes", aTypes,
                          function getAddonsByTypes_concatAddons(aProviderAddons) {
          if (aProviderAddons) {
            addons = addons.concat(aProviderAddons);
          }
          aCaller.callNext();
        });
      },

      noMoreObjects: function(aCaller) {
        safeCall(aCallback, addons);
      }
    });
  },

  /**
   * Asynchronously gets all installed add-ons.
   *
   * @param  aCallback
   *         A callback which will be passed an array of Addons
   */
  getAllAddons: function(aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    this.getAddonsByTypes(null, aCallback);
  },

  /**
   * Asynchronously gets add-ons that have operations waiting for an application
   * restart to complete.
   *
   * @param  aTypes
   *         An optional array of types to retrieve. Each type is a string name
   * @param  aCallback
   *         The callback to pass the array of Addons to
   * @throws if the aCallback argument is not specified
   */
  getAddonsWithOperationsByTypes: function(aTypes, aCallback) {
    if (!gStarted)
      throw Components.Exception("AddonManager is not initialized",
                                 Cr.NS_ERROR_NOT_INITIALIZED);

    if (aTypes && !Array.isArray(aTypes))
      throw Components.Exception("aTypes must be an array or null",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (typeof aCallback != "function")
      throw Components.Exception("aCallback must be a function",
                                 Cr.NS_ERROR_INVALID_ARG);

    let addons = [];

    new AsyncObjectCaller(this.providers, "getAddonsWithOperationsByTypes", {
      nextObject: function(aCaller, aProvider) {
        callProviderAsync(aProvider, "getAddonsWithOperationsByTypes", aTypes,
                          function getAddonsWithOperationsByTypes_concatAddons
                                   (aProviderAddons) {
          if (aProviderAddons) {
            addons = addons.concat(aProviderAddons);
          }
          aCaller.callNext();
        });
      },

      noMoreObjects: function(caller) {
        safeCall(aCallback, addons);
      }
    });
  },

  /**
   * Adds a new AddonManagerListener if the listener is not already registered.
   *
   * @param  aListener
   *         The listener to add
   */
  addManagerListener: function(aListener) {
    if (!aListener || typeof aListener != "object")
      throw Components.Exception("aListener must be an AddonManagerListener object",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!this.managerListeners.some(function addManagerListener_matchListener(i) {
      return i == aListener; }))
      this.managerListeners.push(aListener);
  },

  /**
   * Removes an AddonManagerListener if the listener is registered.
   *
   * @param  aListener
   *         The listener to remove
   */
  removeManagerListener: function(aListener) {
    if (!aListener || typeof aListener != "object")
      throw Components.Exception("aListener must be an AddonManagerListener object",
                                 Cr.NS_ERROR_INVALID_ARG);

    let pos = 0;
    while (pos < this.managerListeners.length) {
      if (this.managerListeners[pos] == aListener)
        this.managerListeners.splice(pos, 1);
      else
        pos++;
    }
  },

  /**
   * Adds a new AddonListener if the listener is not already registered.
   *
   * @param  aListener
   *         The AddonListener to add
   */
  addAddonListener: function(aListener) {
    if (!aListener || typeof aListener != "object")
      throw Components.Exception("aListener must be an AddonListener object",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!this.addonListeners.some(function addAddonListener_matchListener(i) {
      return i == aListener; }))
      this.addonListeners.push(aListener);
  },

  /**
   * Removes an AddonListener if the listener is registered.
   *
   * @param  aListener
   *         The AddonListener to remove
   */
  removeAddonListener: function(aListener) {
    if (!aListener || typeof aListener != "object")
      throw Components.Exception("aListener must be an AddonListener object",
                                 Cr.NS_ERROR_INVALID_ARG);

    let pos = 0;
    while (pos < this.addonListeners.length) {
      if (this.addonListeners[pos] == aListener)
        this.addonListeners.splice(pos, 1);
      else
        pos++;
    }
  },

  /**
   * Adds a new TypeListener if the listener is not already registered.
   *
   * @param  aListener
   *         The TypeListener to add
   */
  addTypeListener: function(aListener) {
    if (!aListener || typeof aListener != "object")
      throw Components.Exception("aListener must be a TypeListener object",
                                 Cr.NS_ERROR_INVALID_ARG);

    if (!this.typeListeners.some(function addTypeListener_matchListener(i) {
      return i == aListener; }))
      this.typeListeners.push(aListener);
  },

  /**
   * Removes an TypeListener if the listener is registered.
   *
   * @param  aListener
   *         The TypeListener to remove
   */
  removeTypeListener: function(aListener) {
    if (!aListener || typeof aListener != "object")
      throw Components.Exception("aListener must be a TypeListener object",
                                 Cr.NS_ERROR_INVALID_ARG);

    let pos = 0;
    while (pos < this.typeListeners.length) {
      if (this.typeListeners[pos] == aListener)
        this.typeListeners.splice(pos, 1);
      else
        pos++;
    }
  },

  get addonTypes() {
    // A read-only wrapper around the types dictionary
    return new Proxy(this.types, {
      defineProperty(target, property, descriptor) {
        // Not allowed to define properties
        return false;
      },

      deleteProperty(target, property) {
        // Not allowed to delete properties
        return false;
      },

      get(target, property, receiver) {
        if (!target.hasOwnProperty(property))
          return undefined;

        return target[property].type;
      },

      getOwnPropertyDescriptor(target, property) {
        if (!target.hasOwnProperty(property))
          return undefined;

        return {
          value: target[property].type,
          writable: false,
          // Claim configurability to maintain the proxy invariants.
          configurable: true,
          enumerable: true
        }
      },

      preventExtensions(target) {
        // Not allowed to prevent adding new properties
        return false;
      },

      set(target, property, value, receiver) {
        // Not allowed to set properties
        return false;
      },

      setPrototypeOf(target, prototype) {
        // Not allowed to change prototype
        return false;
      }
    });
  },

  get autoUpdateDefault() {
    return gAutoUpdateDefault;
  },

  set autoUpdateDefault(aValue) {
    aValue = !!aValue;
    if (aValue != gAutoUpdateDefault)
      Services.prefs.setBoolPref(PREF_EM_AUTOUPDATE_DEFAULT, aValue);
    return aValue;
  },

  get checkCompatibility() {
    return gCheckCompatibility;
  },

  set checkCompatibility(aValue) {
    aValue = !!aValue;
    if (aValue != gCheckCompatibility) {
      if (!aValue)
        Services.prefs.setBoolPref(PREF_EM_CHECK_COMPATIBILITY, false);
      else
        Services.prefs.clearUserPref(PREF_EM_CHECK_COMPATIBILITY);
    }
    return aValue;
  },

  get strictCompatibility() {
    return gStrictCompatibility;
  },

  set strictCompatibility(aValue) {
    aValue = !!aValue;
    if (aValue != gStrictCompatibility)
      Services.prefs.setBoolPref(PREF_EM_STRICT_COMPATIBILITY, aValue);
    return aValue;
  },

  get checkUpdateSecurityDefault() {
    return gCheckUpdateSecurityDefault;
  },

  get checkUpdateSecurity() {
    return gCheckUpdateSecurity;
  },

  set checkUpdateSecurity(aValue) {
    aValue = !!aValue;
    if (aValue != gCheckUpdateSecurity) {
      if (aValue != gCheckUpdateSecurityDefault)
        Services.prefs.setBoolPref(PREF_EM_CHECK_UPDATE_SECURITY, aValue);
      else
        Services.prefs.clearUserPref(PREF_EM_CHECK_UPDATE_SECURITY);
    }
    return aValue;
  },

  get updateEnabled() {
    return gUpdateEnabled;
  },

  set updateEnabled(aValue) {
    aValue = !!aValue;
    if (aValue != gUpdateEnabled)
      Services.prefs.setBoolPref(PREF_EM_UPDATE_ENABLED, aValue);
    return aValue;
  },
};

/**
 * Should not be used outside of core Mozilla code. This is a private API for
 * the startup and platform integration code to use. Refer to the methods on
 * AddonManagerInternal for documentation however note that these methods are
 * subject to change at any time.
 */
this.AddonManagerPrivate = {
  startup: function() {
    AddonManagerInternal.startup();
  },

  registerProvider: function(aProvider, aTypes) {
    AddonManagerInternal.registerProvider(aProvider, aTypes);
  },

  unregisterProvider: function(aProvider) {
    AddonManagerInternal.unregisterProvider(aProvider);
  },

  markProviderSafe: function(aProvider) {
    AddonManagerInternal.markProviderSafe(aProvider);
  },

  backgroundUpdateCheck: function() {
    return AddonManagerInternal.backgroundUpdateCheck();
  },

  backgroundUpdateTimerHandler() {
    // Don't call through to the real update check if no checks are enabled.
    if (!AddonManagerInternal.updateEnabled) {
      logger.info("Skipping background update check");
      return;
    }
    // Don't return the promise here, since the caller doesn't care.
    AddonManagerInternal.backgroundUpdateCheck();
  },

  addStartupChange: function(aType, aID) {
    AddonManagerInternal.addStartupChange(aType, aID);
  },

  removeStartupChange: function(aType, aID) {
    AddonManagerInternal.removeStartupChange(aType, aID);
  },

  notifyAddonChanged: function(aID, aType, aPendingRestart) {
    AddonManagerInternal.notifyAddonChanged(aID, aType, aPendingRestart);
  },

  updateAddonAppDisabledStates: function() {
    AddonManagerInternal.updateAddonAppDisabledStates();
  },

  updateAddonRepositoryData: function(aCallback) {
    AddonManagerInternal.updateAddonRepositoryData(aCallback);
  },

  callInstallListeners: function(...aArgs) {
    return AddonManagerInternal.callInstallListeners.apply(AddonManagerInternal,
                                                           aArgs);
  },

  callAddonListeners: function(...aArgs) {
    AddonManagerInternal.callAddonListeners.apply(AddonManagerInternal, aArgs);
  },

  AddonAuthor: AddonAuthor,

  AddonScreenshot: AddonScreenshot,

  AddonCompatibilityOverride: AddonCompatibilityOverride,

  AddonType: AddonType,

  recordTimestamp: function(name, value) {