themes: add private-autocomplete* styles

platform/toolkit/themes/linux/global/autocomplete.css

@@ -47,6 +47,8 @@ textbox:not(.padded) .textbox-input-box {
 
 panel[type="autocomplete"],
 panel[type="autocomplete-richlistbox"],
+panel[type="private-autocomplete"],
+panel[type="private-autocomplete-richlistbox"],
 .autocomplete-history-popup {
   border: 1px solid ThreeDShadow;
   padding: 0;

platform/toolkit/themes/windows/global/autocomplete.css

@@ -37,6 +37,8 @@ textbox:not(.padded) .textbox-input-box {
 
 panel[type="autocomplete"],
 panel[type="autocomplete-richlistbox"],
+panel[type="private-autocomplete"],
+panel[type="private-autocomplete-richlistbox"],
 .autocomplete-history-popup {
   -moz-appearance: none;
   border-width: 1px;