Remove unnecessary NULL check in DOMWindow::top()

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 1244 matching lines @@
         return parent->domWindow();
 
     return m_frame->domWindow();
 }
 
 DOMWindow* DOMWindow::top() const
 {
     if (!m_frame)
         return 0;
 
-    Page* page = m_frame->page();
-    if (!page)
-        return 0;
-
     return m_frame->tree().top()->domWindow();
 }
 
 Document* DOMWindow::document() const
 {
     return m_document.get();
 }
 
 StyleMedia& DOMWindow::styleMedia() const
 {
@@ skipping 605 matching lines @@
     visitor->trace(m_media);
     visitor->trace(m_sessionStorage);
     visitor->trace(m_localStorage);
     visitor->trace(m_applicationCache);
     visitor->trace(m_performance);
     visitor->trace(m_css);
     WillBeHeapSupplementable<DOMWindow>::trace(visitor);
 }
 
 } // namespace WebCore