Remove several calls to Page::mainFrame

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 1680 matching lines @@
 }
 
 bool InspectorDOMAgent::isWhitespace(Node* node)
 {
     //TODO: pull ignoreWhitespace setting from the frontend and use here.
     return node && node->nodeType() == Node::TEXT_NODE && node->nodeValue().stripWhiteSpace().length() == 0;
 }
 
 void InspectorDOMAgent::domContentLoadedEventFired(Frame* frame)
 {
-    if (frame->page()->mainFrame() != frame)
+    if (!frame->isMainFrame())
         return;
 
     // Re-push document once it is loaded.
     discardFrontendBindings();
     if (m_state->getBoolean(DOMAgentState::documentRequested))
         m_frontend->documentUpdated();
 }
 
 void InspectorDOMAgent::invalidateFrameOwnerElement(Frame* frame)
 {
@@ skipping 11 matching lines @@
     unbind(frameOwner, &m_documentNodeToIdMap);
 
     RefPtr<TypeBuilder::DOM::Node> value = buildObjectForNode(frameOwner, 0, &m_documentNodeToIdMap);
     Node* previousSibling = innerPreviousSibling(frameOwner);
     int prevId = previousSibling ? m_documentNodeToIdMap.get(previousSibling) : 0;
     m_frontend->childNodeInserted(parentId, prevId, value.release());
 }
 
 void InspectorDOMAgent::didCommitLoad(Frame* 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.
     Frame* mainFrame = frame->page()->mainFrame();
     if (loader->frame() != mainFrame) {
         invalidateFrameOwnerElement(loader->frame());
         return;
     }
 
     setDocument(mainFrame->document());
 }
 
 void InspectorDOMAgent::didInsertDOMNode(Node* node)
@@ skipping 294 matching lines @@
     if (!m_documentNodeToIdMap.contains(m_document)) {
         RefPtr<TypeBuilder::DOM::Node> root;
         getDocument(errorString, root);
         return errorString->isEmpty();
     }
     return true;
 }
 
 } // namespace WebCore