Handle LocalFrame being nestedly detached by subframe.

Source/core/frame/LocalFrame.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 263 matching lines @@
 
 void LocalFrame::detach(FrameDetachType type)
 {
     PluginScriptForbiddenScope forbidPluginDestructorScripting;
     // A lot of the following steps can result in the current frame being
     // detached, so protect a reference to it.
     RefPtrWillBeRawPtr<LocalFrame> protect(this);
     m_loader.stopAllLoaders();
     m_loader.dispatchUnloadEvent();
     detachChildren();
+
+    // All done if detaching the subframes brought about a detach of this frame also.
+    if (!client())
+        return;
+
     // stopAllLoaders() needs to be called after detachChildren(), because detachChildren()
     // will trigger the unload event handlers of any child frames, and those event
     // handlers might start a new subresource load in this frame.
     m_loader.stopAllLoaders();
     m_loader.detach();
     document()->detach();
     m_loader.clear();
     if (!client())
         return;
 
@@ skipping 553 matching lines @@
 {
     if (isLocalRoot())
         m_instrumentingAgents = InstrumentingAgents::create();
     else
         m_instrumentingAgents = localFrameRoot()->m_instrumentingAgents;
 }
 
 DEFINE_WEAK_IDENTIFIER_MAP(LocalFrame);
 
 } // namespace blink