Bug 467828 - use cached favicons for the Recently Closed Tabs menu. r=gavin

browser/base/content/browser.js

@@ -6204,8 +6204,13 @@ HistoryMenu.populateUndoSubmenu = function PHM_populateUndoSubmenu() {
   for (var i = 0; i < undoItems.length; i++) {
     var m = document.createElement("menuitem");
     m.setAttribute("label", undoItems[i].title);
-    if (undoItems[i].image)
-      m.setAttribute("image", undoItems[i].image);
+    if (undoItems[i].image) {
+      let iconURL = undoItems[i].image;
+      // don't initiate a connection just to fetch a favicon (see bug 467828)
+      if (/^https?:/.test(iconURL))
+        iconURL = "moz-anno:favicon:" + iconURL;
+      m.setAttribute("image", iconURL);
+    }
     m.setAttribute("class", "menuitem-iconic bookmark-item");
     m.setAttribute("value", i);
     m.setAttribute("oncommand", "undoCloseTab(" + i + ");");