Add Frame::isMainFrame and deploy it

Source/core/loader/FrameLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Kris Jordan <krisjordan@gmail.com>
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ skipping 892 matching lines @@
     // use a recursive algorithm here.
     for (Frame* child = m_frame->tree().firstChild(); child; child = child->tree().nextSibling())
         child->loader().closeOldDataSources();
 
     if (m_documentLoader)
         m_client->dispatchWillClose();
 }
 
 bool FrameLoader::isLoadingMainFrame() const
 {
-    Page* page = m_frame->page();
-    return page && m_frame == page->mainFrame();
+    return m_frame->isMainFrame();
 }
 
 bool FrameLoader::subframeIsLoading() const
 {
     // It's most likely that the last added frame is the last to load so we walk backwards.
     for (Frame* child = m_frame->tree().lastChild(); child; child = child->tree().previousSibling()) {
         const FrameLoader& childLoader = child->loader();
         DocumentLoader* documentLoader = childLoader.documentLoader();
         if (documentLoader && documentLoader->isLoadingInAPISense())
             return true;
@@ skipping 649 matching lines @@
 {
     SandboxFlags flags = m_forcedSandboxFlags;
     if (Frame* parentFrame = m_frame->tree().parent())
         flags |= parentFrame->document()->sandboxFlags();
     if (HTMLFrameOwnerElement* ownerElement = m_frame->ownerElement())
         flags |= ownerElement->sandboxFlags();
     return flags;
 }
 
 } // namespace WebCore