Match html canvas which is transferred to OffscreenCanvas to CSS style

cc/layers/surface_layer_impl.h

 // Copyright 2014 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_LAYERS_SURFACE_LAYER_IMPL_H_
 #define CC_LAYERS_SURFACE_LAYER_IMPL_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "cc/base/cc_export.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/surfaces/surface_id.h"
 
 namespace cc {
 
 class CC_EXPORT SurfaceLayerImpl : public LayerImpl {
  public:
   static std::unique_ptr<SurfaceLayerImpl> Create(LayerTreeImpl* tree_impl,
                                                   int id) {
     return base::WrapUnique(new SurfaceLayerImpl(tree_impl, id));
   }
   ~SurfaceLayerImpl() override;
 
   void SetSurfaceId(const SurfaceId& surface_id);
   void SetSurfaceScale(float scale);
   void SetSurfaceSize(const gfx::Size& size);
+  void SetStretchContentToFillBounds(bool is_scaling_needed);

[danakj, 2016/12/15 16:13:14]

nit: name the var stretch_content?

   const SurfaceId& surface_id() const { return surface_id_; }
 
   // LayerImpl overrides.
   std::unique_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override;
   void PushPropertiesTo(LayerImpl* layer) override;
   void AppendQuads(RenderPass* render_pass,
                    AppendQuadsData* append_quads_data) override;
 
  protected:
   SurfaceLayerImpl(LayerTreeImpl* tree_impl, int id);
 
  private:
   void GetDebugBorderProperties(SkColor* color, float* width) const override;
   void AppendRainbowDebugBorder(RenderPass* render_pass);
   void AsValueInto(base::trace_event::TracedValue* dict) const override;
   const char* LayerTypeAsString() const override;
 
   SurfaceId surface_id_;
   gfx::Size surface_size_;
-  float surface_scale_;
+  float surface_scale_ = 0.f;
+  bool stretch_content_to_fill_bounds_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceLayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_SURFACE_LAYER_IMPL_H_