[DevTools] Cleanup DOMExtension.js.

third_party/WebKit/Source/devtools/front_end/main/Main.js

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2007 Matt Lilek (pewtermoose@gmail.com).
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * 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
@@ skipping 454 matching lines @@
             ];
             section.addRelatedKeys(keys, WebInspector.UIString("Find next/previous"));
         }
     },
 
     _postDocumentKeyDown: function(event)
     {
         if (event.handled)
             return;
 
-        var target = event.deepActiveElement();
+        var document = event.target && event.target.ownerDocument;
+        var target = document ? document.deepActiveElement() : null;
         if (target) {
             var anchor = target.enclosingNodeOrSelfWithNodeName("a");
             if (anchor && anchor.preventFollow)
                 event.preventDefault();
         }
 
         if (!WebInspector.Dialog.hasInstance() && WebInspector.inspectorView.currentPanel()) {
             WebInspector.inspectorView.currentPanel().handleShortcut(event);
             if (event.handled) {
                 event.consume(true);
                 return;
             }
         }
 
         WebInspector.shortcutRegistry.handleShortcut(event);
     },
 
     /**
      * @param {!Event} event
      */
     _redispatchClipboardEvent: function(event)
     {
         var eventCopy = new CustomEvent("clipboard-" + event.type);
         eventCopy["original"] = event;
-        event.deepActiveElement().dispatchEvent(eventCopy);
+        var document = event.target && event.target.ownerDocument;
+        var target = document ? document.deepActiveElement() : null;
+        if (target)
+            target.dispatchEvent(eventCopy);
         if (eventCopy.handled)
             event.preventDefault();
     },
 
     _contextMenuEventFired: function(event)
     {
         if (event.handled || event.target.classList.contains("popup-glasspane"))
             event.preventDefault();
     },
 
@@ skipping 599 matching lines @@
      * @override
      * @return {?Element}
      */
     settingElement: function()
     {
         return WebInspector.SettingsUI.createSettingCheckbox(WebInspector.UIString("Show rulers"), WebInspector.moduleSetting("showMetricsRulers"));
     }
 }
 
 new WebInspector.Main();