remove unused cachedBitmap from ImageBufferSurface

Source/platform/graphics/ImageBufferSurface.cpp

 /*
  * Copyright (c) 2013, Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 58 matching lines @@
     }
 }
 
 const SkBitmap& ImageBufferSurface::bitmap()
 {
     ASSERT(canvas());
     willAccessPixels();
     return canvas()->getDevice()->accessBitmap(false);
 }
 
-const SkBitmap& ImageBufferSurface::cachedBitmap() const
-{
-    DEFINE_STATIC_LOCAL(SkBitmap, nullBitmap, ());
-    return nullBitmap;
-}
-
 void ImageBufferSurface::draw(GraphicsContext* context, const FloatRect& destRect, const FloatRect& srcRect, SkXfermode::Mode op)
 {
     SkBitmap bmp = bitmap();
-    // For ImageBufferSurface that enables cachedBitmap, Use the cached bitmap for CPU side usage
-    // if it is available, otherwise generate and use it.
-    if (isAccelerated() && cachedBitmapEnabled() && isValid()) {
-        updateCachedBitmapIfNeeded();
-        bmp = cachedBitmap();
-    }
 
     RefPtr<Image> image = BitmapImage::create(bmp);
 
     context->drawImage(image.get(), destRect, srcRect, op, DoNotRespectImageOrientation);
 }
 
 } // namespace blink