Add Frame::isMainFrame and deploy it

Source/core/rendering/RenderView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 1191 matching lines @@
 IntervalArena* RenderView::intervalArena()
 {
     if (!m_intervalArena)
         m_intervalArena = IntervalArena::create();
     return m_intervalArena.get();
 }
 
 bool RenderView::backgroundIsKnownToBeOpaqueInRect(const LayoutRect&) const
 {
     // FIXME: Remove this main frame check. Same concept applies to subframes too.
-    Page* page = document().page();
-    Frame* mainFrame = page ? page->mainFrame() : 0;
-    if (!m_frameView || &m_frameView->frame() != mainFrame)
+    if (!m_frameView || !m_frameView->isMainFrame())
         return false;
 
     return m_frameView->hasOpaqueBackground();
 }
 
 LayoutUnit RenderView::viewportPercentageWidth(float percentage) const
 {
     return viewLogicalWidth(ScrollableArea::IncludeScrollbars) * percentage / 100.f;
 }
 
@@ skipping 46 matching lines @@
 #endif
 
     if (layoutState)
         layoutState->m_isPaginated = m_fragmenting;
 
     if (m_flowThreadState != RenderObject::NotInsideFlowThread)
         m_root->setFlowThreadStateIncludingDescendants(m_flowThreadState);
 }
 
 } // namespace WebCore