Bug 1217129: Part 1 - Add onDestroyed callback to CustomizableUI widgets. r=gijs

--HG--
extra : commitid : vNV77IiNAr
extra : rebase_source : fdf99396467cc54cfe3605cddf6db415fb44f077
extra : source : 93266f211716db6c1b5782e6e8d5803baaae1d27

browser/components/customizableui/CustomizableUI.jsm

@@ -2336,6 +2336,7 @@ var CustomizableUIInternal = {
     this.wrapWidgetEventHandler("onBeforeCreated", widget);
     this.wrapWidgetEventHandler("onClick", widget);
     this.wrapWidgetEventHandler("onCreated", widget);
+    this.wrapWidgetEventHandler("onDestroyed", widget);
 
     if (widget.type == "button") {
       widget.onCommand = typeof aData.onCommand == "function" ?
@@ -2439,6 +2440,9 @@ var CustomizableUIInternal = {
           }
         }
       }
+      if (widgetNode && widget.onDestroyed) {
+        widget.onDestroyed(window.document);
+      }
     }
 
     gPalette.delete(aWidgetId);
@@ -3172,6 +3176,11 @@ this.CustomizableUI = {
    * - onCreated(aNode): Attached to all widgets; a function that will be invoked
    *                  whenever the widget has a DOM node constructed, passing the
    *                  constructed node as an argument.
+   * - onDestroyed(aDoc): Attached to all non-custom widgets; a function that
+   *                  will be invoked after the widget has a DOM node destroyed,
+   *                  passing the document from which it was removed. This is
+   *                  useful especially for 'view' type widgets that need to
+   *                  cleanup after views that were constructed on the fly.
    * - onCommand(aEvt): Only useful for button widgets; a function that will be
    *                    invoked when the user activates the button.
    * - onClick(aEvt): Attached to all widgets; a function that will be invoked