[DevTools] Cleanup DOMExtension.js.

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

Index: third_party/WebKit/Source/devtools/front_end/main/Main.js
diff --git a/third_party/WebKit/Source/devtools/front_end/main/Main.js b/third_party/WebKit/Source/devtools/front_end/main/Main.js
index fe64fce912d4c92244e05772c91443a442a21a2b..db6c229cab60970b3b7145588bf676797b6e38f5 100644
--- a/third_party/WebKit/Source/devtools/front_end/main/Main.js
+++ b/third_party/WebKit/Source/devtools/front_end/main/Main.js
@@ -472,7 +472,8 @@ WebInspector.Main.prototype = {
         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)
@@ -497,7 +498,10 @@ WebInspector.Main.prototype = {
     {
         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();
     },