Add support for accelerated fixed root background

Source/WebCore/page/Settings.h

 /*
  * Copyright (C) 2003, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * 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
@@ skipping 107 matching lines @@
         // the image URL.  A cached image will still be rendered if requested.
         void setLoadsImagesAutomatically(bool);
         bool loadsImagesAutomatically() const { return m_loadsImagesAutomatically; }
 
         // Clients that execute script should call ScriptController::canExecuteScripts()
         // instead of this function. ScriptController::canExecuteScripts() checks the
         // HTML sandbox, plug-in sandboxing, and other important details.
         bool isScriptEnabled() const { return m_isScriptEnabled; }
         void setScriptEnabled(bool);
 
+        // NB: This define is generated by a script. To add a new setting, you
+        // need to modify the script's input, Settings.in.
         SETTINGS_GETTERS_AND_SETTERS
 
         void setJavaEnabled(bool);
         bool isJavaEnabled() const { return m_isJavaEnabled; }
 
         // This settings is only consulted if isJavaEnabled() returns true;
         void setJavaEnabledForLocalFiles(bool);
         bool isJavaEnabledForLocalFiles() const { return m_isJavaEnabledForLocalFiles; }
 
         void setImagesEnabled(bool);
@@ skipping 222 matching lines @@
 #if USE(JSC)
         static bool gShouldRespectPriorityInCSSAttributeSetters;
 #endif
 
         static double gHiddenPageDOMTimerAlignmentInterval;
     };
 
 } // namespace WebCore
 
 #endif // Settings_h