Scale the ALPHA_THRESHOLD filter's region based on the device scale factor.

cc/output/render_surface_filters.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 
 #ifndef CC_OUTPUT_RENDER_SURFACE_FILTERS_H_
 #define CC_OUTPUT_RENDER_SURFACE_FILTERS_H_
 
 #include "base/basictypes.h"
 #include "cc/base/cc_export.h"
 #include "skia/ext/refptr.h"
 
 class GrContext;
 class SkBitmap;
 class SkImageFilter;
 
 namespace gfx {
 class SizeF;
+class Vector2dF;
 }
 
 namespace cc {
 
 class FilterOperations;
 
 class CC_EXPORT RenderSurfaceFilters {
  public:
   static SkBitmap Apply(const FilterOperations& filters,
                         unsigned texture_id,
                         const gfx::SizeF& size,
                         GrContext* gr_context);
   static FilterOperations Optimize(const FilterOperations& filters);
 
   static skia::RefPtr<SkImageFilter> BuildImageFilter(
       const FilterOperations& filters,
+      const gfx::Vector2dF& scale,
       const gfx::SizeF& size);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(RenderSurfaceFilters);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_RENDER_SURFACE_FILTERS_H_