Remove observer in destructor. r/sr=hewitt

xpfe/components/bookmarks/resources/bookmarks.js

@@ -77,7 +77,8 @@ function Shutdown ()
   win.setAttribute("height", outerHeight);
   win.setAttribute("width", outerWidth);
 
-  gBookmarksShell.flushDataSource();
+  var bookmarksView = document.getElementById("bookmarks-view");
+  bookmarksView.flushBMDatasource();
 }
 
 function updateSendLinkItem()                                                   

xpfe/components/bookmarks/resources/bookmarks.xml

@@ -95,6 +95,9 @@
         this._bundle = stringBundleService.createBundle(bundleURL, localeService.GetApplicationLocale());
         setTimeout(this.refreshSort, 0, this);
       ]]></constructor>
+      <destructor><![CDATA[
+        this.outlinerBuilder.removeObserver(this.builderObserver);
+      ]]></destructor>
 
       <property name="outlinerBoxObject">
         <getter><![CDATA[