Add Frame::isMainFrame and deploy it

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 2931 matching lines @@
             m_viewportDescription = m_legacyViewportDescription;
         else
             m_viewportDescription = viewportDescription;
     }
 
     updateViewportDescription();
 }
 
 void Document::updateViewportDescription()
 {
-    if (page() && page()->mainFrame() == frame()) {
+    if (frame()->isMainFrame()) {
 #ifndef NDEBUG
         m_didDispatchViewportPropertiesChanged = true;
 #endif
         page()->chrome().dispatchViewportPropertiesDidChange(m_viewportDescription);
     }
 }
 
 void Document::processReferrerPolicy(const String& policy)
 {
     ASSERT(!policy.isNull());
@@ skipping 2259 matching lines @@
 void Document::modifiedStyleSheet(StyleSheet* sheet, RecalcStyleTime when, StyleResolverUpdateMode updateMode)
 {
     if (!isActive())
         return;
 
     styleEngine()->modifiedStyleSheet(sheet);
     styleResolverChanged(when, updateMode);
 }
 
 } // namespace WebCore