Add toSVGImage fuction, and use it as much as we can.

Source/core/accessibility/AccessibilityRenderObject.cpp

 /*
 * Copyright (C) 2008 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
@@ skipping 2068 matching lines @@
         return 0;
 
     ImageResource* cachedImage = toRenderImage(m_renderer)->cachedImage();
     if (!cachedImage)
         return 0;
 
     Image* image = cachedImage->image();
     if (!image || !image->isSVGImage())
         return 0;
 
-    SVGImage* svgImage = static_cast<SVGImage*>(image);
-    FrameView* frameView = svgImage->frameView();
+    FrameView* frameView = toSVGImage(image)->frameView();
     if (!frameView)
         return 0;
     Document* doc = frameView->frame().document();
     if (!doc || !doc->isSVGDocument())
         return 0;
 
     SVGSVGElement* rootElement = toSVGDocument(doc)->rootElement();
     if (!rootElement)
         return 0;
     RenderObject* rendererRoot = rootElement->renderer();
@@ skipping 275 matching lines @@
         if (label && label->renderer()) {
             LayoutRect labelRect = axObjectCache()->getOrCreate(label)->elementRect();
             result.unite(labelRect);
         }
     }
 
     return result;
 }
 
 } // namespace WebCore