diff -r 000000000000 -r 6474c204b198 toolkit/modules/PageMenu.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/modules/PageMenu.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,139 @@
+/* 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/. */
+
+this.EXPORTED_SYMBOLS = ["PageMenu"];
+
+this.PageMenu = function PageMenu() {
+}
+
+PageMenu.prototype = {
+  PAGEMENU_ATTR: "pagemenu",
+  GENERATEDITEMID_ATTR: "generateditemid",
+
+  popup: null,
+  builder: null,
+
+  maybeBuildAndAttachMenu: function(aTarget, aPopup) {
+    var pageMenu = null;
+    var target = aTarget;
+    while (target) {
+      var contextMenu = target.contextMenu;
+      if (contextMenu) {
+        pageMenu = contextMenu;
+        break;
+      }
+      target = target.parentNode;
+    }
+
+    if (!pageMenu) {
+      return false;
+    }
+
+    var insertionPoint = this.getInsertionPoint(aPopup);
+    if (!insertionPoint) {
+      return false;
+    }
+
+    pageMenu.QueryInterface(Components.interfaces.nsIHTMLMenu);
+    pageMenu.sendShowEvent();
+    // the show event is not cancelable, so no need to check a result here
+
+    var fragment = aPopup.ownerDocument.createDocumentFragment();
+
+    var builder = pageMenu.createBuilder();
+    if (!builder) {
+      return false;
+    }
+    builder.QueryInterface(Components.interfaces.nsIXULContextMenuBuilder);
+    builder.init(fragment, this.GENERATEDITEMID_ATTR);
+
+    pageMenu.build(builder);
+
+    var pos = insertionPoint.getAttribute(this.PAGEMENU_ATTR);
+    if (pos == "start") {
+      insertionPoint.insertBefore(fragment,
+                                  insertionPoint.firstChild);
+    } else {
+      insertionPoint.appendChild(fragment);
+    }
+
+    this.builder = builder;
+    this.popup = aPopup;
+
+    this.popup.addEventListener("command", this);
+    this.popup.addEventListener("popuphidden", this);
+
+    return true;
+  },
+
+  handleEvent: function(event) {
+    var type = event.type;
+    var target = event.target;
+    if (type == "command" && target.hasAttribute(this.GENERATEDITEMID_ATTR)) {
+      this.builder.click(target.getAttribute(this.GENERATEDITEMID_ATTR));
+    } else if (type == "popuphidden" && this.popup == target) {
+      this.removeGeneratedContent(this.popup);
+
+      this.popup.removeEventListener("popuphidden", this);
+      this.popup.removeEventListener("command", this);
+
+      this.popup = null;
+      this.builder = null;
+    }
+  },
+
+  getImmediateChild: function(element, tag) {
+    var child = element.firstChild;
+    while (child) {
+      if (child.localName == tag) {
+        return child;
+      }
+      child = child.nextSibling;
+    }
+    return null;
+  },
+
+  getInsertionPoint: function(aPopup) {
+    if (aPopup.hasAttribute(this.PAGEMENU_ATTR))
+      return aPopup;
+
+    var element = aPopup.firstChild;
+    while (element) {
+      if (element.localName == "menu") {
+        var popup = this.getImmediateChild(element, "menupopup");
+        if (popup) {
+          var result = this.getInsertionPoint(popup);
+          if (result) {
+            return result;
+          }
+        }
+      }
+      element = element.nextSibling;
+    }
+
+    return null;
+  },
+
+  removeGeneratedContent: function(aPopup) {
+    var ungenerated = [];
+    ungenerated.push(aPopup);
+
+    var count;
+    while (0 != (count = ungenerated.length)) {
+      var last = count - 1;
+      var element = ungenerated[last];
+      ungenerated.splice(last, 1);
+
+      var i = element.childNodes.length;
+      while (i-- > 0) {
+        var child = element.childNodes[i];
+        if (!child.hasAttribute(this.GENERATEDITEMID_ATTR)) {
+          ungenerated.push(child);
+          continue;
+        }
+        element.removeChild(child);
+      }
+    }
+  }
+}