Add Blink APIs for frame tree mirroring.

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 296 matching lines @@
 void WebView::didExitModalLoop()
 {
     ASSERT(pageLoadDeferrerStack().size());
 
     delete pageLoadDeferrerStack().last();
     pageLoadDeferrerStack().removeLast();
 }
 
 void WebViewImpl::setMainFrame(WebFrame* frame)
 {
-    toWebLocalFrameImpl(frame)->initializeAsMainFrame(page());
+    frame->initializeAsMainFrame(this);
 }
 
 void WebViewImpl::setAutofillClient(WebAutofillClient* autofillClient)
 {
     m_autofillClient = autofillClient;
 }
 
 void WebViewImpl::setDevToolsAgentClient(WebDevToolsAgentClient* devToolsClient)
 {
     if (devToolsClient)
@@ skipping 3776 matching lines @@
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return false;
 
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace blink