Add Frame::isMainFrame and deploy it

Source/core/css/FontFaceSet.cpp

 /*
  * Copyright (C) 2013 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:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 159 matching lines @@
 
 void FontFaceSet::handlePendingEventsAndPromisesSoon()
 {
     // setPendingActivity() is unnecessary because m_asyncRunner will be
     // automatically stopped on destruction.
     m_asyncRunner.runAsync();
 }
 
 void FontFaceSet::didLayout()
 {
-    Document* d = document();
-    if (d->page() && d->page()->mainFrame() == d->frame())
+    if (document()->frame()->isMainFrame())
         m_histogram.record();
     if (!RuntimeEnabledFeatures::fontLoadEventsEnabled())
         return;
     if (m_loadingCount || (!hasLoadedFonts() && m_readyResolvers.isEmpty()))
         return;
     handlePendingEventsAndPromisesSoon();
 }
 
 void FontFaceSet::handlePendingEventsAndPromises()
 {
@@ skipping 264 matching lines @@
 }
 
 void FontFaceSet::didLayout(Document* document)
 {
     if (FontFaceSet* fonts = static_cast<FontFaceSet*>(SupplementType::from(document, supplementName())))
         fonts->didLayout();
 }
 
 
 } // namespace WebCore