Remove the acceleratedCompositingForCanvas setting.

Source/core/rendering/RenderPart.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  *           (C) 2000 Stefan Schimanski (1Stein@gmx.de)
  * Copyright (C) 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. 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
@@ skipping 109 matching lines @@
             // FIXME: Consider if this test could be done unconditionally.
             Scrollbar* frameScrollbar = childFrameView->scrollbarAtPoint(newHitTestLocation.roundedPoint());
             if (frameScrollbar)
                 result.setScrollbar(frameScrollbar);
         }
     }
 
     return RenderWidget::nodeAtPoint(request, result, locationInContainer, accumulatedOffset, action);
 }
 
-CompositingReasons RenderPart::additionalCompositingReasons(CompositingTriggerFlags) const
+CompositingReasons RenderPart::additionalCompositingReasons() const
 {
     if (requiresAcceleratedCompositing())
         return CompositingReasonIFrame;
     return CompositingReasonNone;
 }
 
 }