Change Page::m_mainFrame to be a Frame.

Source/core/inspector/InspectorDOMAgent.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * 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
@@ skipping 1759 matching lines @@
     Node* previousSibling = innerPreviousSibling(frameOwner);
     int prevId = previousSibling ? m_documentNodeToIdMap->get(previousSibling) : 0;
     m_frontend->childNodeInserted(parentId, prevId, value.release());
 }
 
 void InspectorDOMAgent::didCommitLoad(LocalFrame* frame, DocumentLoader* loader)
 {
     // FIXME: If "frame" is always guarenteed to be in the same Page as loader->frame()
     // then all we need to check here is loader->frame()->isMainFrame()
     // and we don't need "frame" at all.
-    LocalFrame* mainFrame = frame->page()->mainFrame();
+    Frame* mainFrame = frame->page()->mainFrame();
     if (loader->frame() != mainFrame) {
         invalidateFrameOwnerElement(loader->frame());
         return;
     }
 
-    setDocument(mainFrame->document());
+    setDocument(mainFrame->isLocalFrame() ? toLocalFrame(mainFrame)->document() : 0);
 }
 
 void InspectorDOMAgent::didInsertDOMNode(Node* node)
 {
     if (isWhitespace(node))
         return;
 
     // We could be attaching existing subtree. Forget the bindings.
     unbind(node, m_documentNodeToIdMap.get());
 
@@ skipping 299 matching lines @@
     if (!m_documentNodeToIdMap->contains(m_document.get())) {
         RefPtr<TypeBuilder::DOM::Node> root;
         getDocument(errorString, root);
         return errorString->isEmpty();
     }
     return true;
 }
 
 } // namespace WebCore