Fix display list canvas not rendering correctly on high dpi displays

Source/platform/graphics/ImageBuffer.cpp

 /*
  * Copyright (c) 2008, Google Inc. All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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
@@ skipping 247 matching lines @@
 
     return result;
 }
 
 void ImageBuffer::draw(GraphicsContext* context, const FloatRect& destRect, const FloatRect* srcPtr, CompositeOperator op, WebBlendMode blendMode)
 {
     if (!isSurfaceValid())
         return;
 
     FloatRect srcRect = srcPtr ? *srcPtr : FloatRect(FloatPoint(), size());
     RefPtr<SkPicture> picture = m_surface->getPicture();

[Stephen White, 2014/12/12 22:14:12]

IWBN if the SkPicture-related stuff could all live in the surface, if possible,
and not be exposed at the ImageBuffer level.

Maybe we could have a draw(GraphicsContext* context, ...) virtual on
ImageBufferSurface? Just a thought.

[Justin Novosad, 2014/12/12 22:31:51]

Acknowledged.

     if (picture) {
-        context->drawPicture(picture.get(), destRect, srcRect, op, blendMode);
+        context->compositePicture(picture.get(), destRect, srcRect, op, blendMode);
         return;
     }
 
     SkBitmap bitmap = m_surface->bitmap();
     // For ImageBufferSurface that enables cachedBitmap, Use the cached Bitmap for CPU side usage
     // if it is available, otherwise generate and use it.
     if (!context->isAccelerated() && m_surface->isAccelerated() && m_surface->cachedBitmapEnabled() && isSurfaceValid()) {
         m_surface->updateCachedBitmapIfNeeded();
         bitmap = m_surface->cachedBitmap();
     }
@@ skipping 129 matching lines @@
 
 String ImageBuffer::toDataURL(const String& mimeType, const double* quality) const
 {
     if (!isSurfaceValid())
         return "data:,";
 
     return ImageEncoder::toDataURL(m_surface->bitmap(), mimeType, quality);
 }
 
 } // namespace blink