Reland of DevTools: automatically populate 'More tools' submenu with the drawer views.

third_party/WebKit/Source/devtools/front_end/ui/SoftContextMenu.js

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 373 matching lines @@
         if (this._discardMenuOnResizeListener) {
             this._document.defaultView.removeEventListener("resize", this._discardMenuOnResizeListener, false);
             delete this._discardMenuOnResizeListener;
         }
     },
 
     _discardSubMenus: function()
     {
         if (this._subMenu)
             this._subMenu._discardSubMenus();
-        this.element.remove();
+        if (this.element)
+            this.element.remove();
         if (this._parentMenu)
             delete this._parentMenu._subMenu;
     }
 }