Add support for accelerated fixed root background

Source/core/page/Frame.h

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999-2001 Lars Knoll <knoll@kde.org>
  *                     1999-2001 Antti Koivisto <koivisto@kde.org>
  *                     2000-2001 Simon Hausmann <hausmann@kde.org>
  *                     2000-2001 Dirk Mueller <mueller@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
@@ skipping 48 matching lines @@
     class ScriptController;
     class Settings;
     class TreeScope;
     class VisiblePosition;
 
     enum {
         LayerTreeFlagsIncludeDebugInfo = 1 << 0,
         LayerTreeFlagsIncludeVisibleRects = 1 << 1,
         LayerTreeFlagsIncludeTileCaches = 1 << 2,
         LayerTreeFlagsIncludeRepaintRects = 1 << 3,
-        LayerTreeFlagsIncludePaintingPhases = 1 << 4
+        LayerTreeFlagsIncludePaintingPhases = 1 << 4,
+        LayerTreeFlagsIncludeRootLayer = 1 << 5
     };
     typedef unsigned LayerTreeFlags;
 
     class Frame : public RefCounted<Frame> {
     public:
         static PassRefPtr<Frame> create(Page*, HTMLFrameOwnerElement*, FrameLoaderClient*);
 
         void init();
         void setView(PassRefPtr<FrameView>);
         void createView(const IntSize&, const Color&, bool,
@@ skipping 194 matching lines @@
     }
 
     inline EventHandler* Frame::eventHandler() const
     {
         return m_eventHandler.get();
     }
 
 } // namespace WebCore
 
 #endif // Frame_h