Fix frameElement for frames with a remote parent.

Source/core/frame/LocalDOMWindow.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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
@@ skipping 715 matching lines @@
 DOMSelection* LocalDOMWindow::getSelection()
 {
     if (!isCurrentlyDisplayedInFrame())
         return nullptr;
 
     return frame()->document()->getSelection();
 }
 
 Element* LocalDOMWindow::frameElement() const
 {
-    if (!frame())
+    if (!frame() || (frame()->owner() && !frame()->owner()->isLocal()))

[alexmos, 2015/04/30 20:45:26]

The comment about the binding security check below implies that frameElement()
is expected to be called only when the frame and parent are same-origin.  Do we
want to keep this, or should we return nullptr for the remote case as opposed to
hitting the ASSERT below?  The fix in this CL doesn't need this change; I'm just
curious what you think.

[dcheng, 2015/04/30 20:58:51]

I'd prefer to just hit the assert below. deprecatedLocalOwner() will also assert
(though since we're in this code, it might be good to just change that to
toHTMLFrameOwnerElement(frame()->owner(), so we know this particular usage is
"kosher").

[alexmos, 2015/04/30 21:12:58]

Sounds good -- done.

         return nullptr;
 
     // The bindings security check should ensure we're same origin...
     ASSERT(!frame()->owner() || frame()->owner()->isLocal());
     return frame()->deprecatedLocalOwner();
 }
 
 void LocalDOMWindow::focus(ExecutionContext* context)
 {
     if (!frame())
@@ skipping 824 matching lines @@
     DOMWindow::trace(visitor);
     DOMWindowLifecycleNotifier::trace(visitor);
 }
 
 LocalFrame* LocalDOMWindow::frame() const
 {
     return m_frameObserver->frame();
 }
 
 } // namespace blink