Add more checks to prevent crashes when accessing name/opener properties

Source/core/frame/DOMWindow.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 1171 matching lines @@
 unsigned DOMWindow::length() const
 {
     if (!isCurrentlyDisplayedInFrame())
         return 0;
 
     return m_frame->tree().scopedChildCount();
 }
 
 const AtomicString& DOMWindow::name() const
 {
-    if (!m_frame)
+    if (!isCurrentlyDisplayedInFrame())
         return nullAtom;
 
     return m_frame->tree().name();
 }
 
 void DOMWindow::setName(const AtomicString& name)
 {
-    if (!m_frame)
+    if (!isCurrentlyDisplayedInFrame())
         return;
 
     m_frame->tree().setName(name);
+    ASSERT(m_frame->loader().client());
     m_frame->loader().client()->didChangeName(name);
 }
 
 void DOMWindow::setStatus(const String& string)
 {
     m_status = string;
 
     if (!m_frame)
         return;
 
@@ skipping 646 matching lines @@
     return static_cast<DOMWindowLifecycleNotifier&>(LifecycleContext<DOMWindow>::lifecycleNotifier());
 }
 
 PassOwnPtr<LifecycleNotifier<DOMWindow> > DOMWindow::createLifecycleNotifier()
 {
     return DOMWindowLifecycleNotifier::create(this);
 }
 
 
 } // namespace WebCore