Introduce toHTMLCanvasElement

Source/core/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple 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 1771 matching lines @@
     }
     return false;
 }
 
 bool RenderLayerCompositor::requiresCompositingForCanvas(RenderObject* renderer) const
 {
     if (!(m_compositingTriggers & ChromeClient::CanvasTrigger))
         return false;
 
     if (renderer->isCanvas()) {
-        HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(renderer->node());
+        HTMLCanvasElement* canvas = toHTMLCanvasElement(renderer->node());
 #if USE(COMPOSITING_FOR_SMALL_CANVASES)
         bool isCanvasLargeEnoughToForceCompositing = true;
 #else
         bool isCanvasLargeEnoughToForceCompositing = canvas->size().area() >= canvasAreaThresholdRequiringCompositing;
 #endif
         return canvas->renderingContext() && canvas->renderingContext()->isAccelerated() && (canvas->renderingContext()->is3d() || isCanvasLargeEnoughToForceCompositing);
     }
     return false;
 }
 
@@ skipping 935 matching lines @@
     info.addMember(m_layerForScrollCorner, "layerForScrollCorner");
 #if ENABLE(RUBBER_BANDING)
     info.addMember(m_layerForOverhangAreas, "layerForOverhangAreas");
     info.addMember(m_contentShadowLayer, "contentShadowLayer");
     info.addMember(m_layerForTopOverhangArea, "layerForTopOverhangArea");
     info.addMember(m_layerForBottomOverhangArea, "layerForBottomOverhangArea");
 #endif
 }
 
 } // namespace WebCore