Match html canvas which is transferred to OffscreenCanvas to CSS style

cc/layers/surface_layer.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_H_
 #define CC_LAYERS_SURFACE_LAYER_H_
 
 #include "base/macros.h"
 #include "cc/base/cc_export.h"
 #include "cc/layers/layer.h"
@@ skipping 14 matching lines @@
 
   // This callback is run to require that a specific SurfaceSequence is
   // received before a SurfaceId is destroyed.
   using RequireCallback =
       base::Callback<void(const SurfaceId&, const SurfaceSequence&)>;
 
   static scoped_refptr<SurfaceLayer> Create(
       const SatisfyCallback& satisfy_callback,
       const RequireCallback& require_callback);
 
+  // When stretch_content_to_fill_bounds is true, scale is unused.
   void SetSurfaceId(const SurfaceId& surface_id,
                     float scale,
-                    const gfx::Size& size);
+                    const gfx::Size& size,
+                    bool stretch_content_to_fill_bounds);
 
   // Layer overrides.
   std::unique_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override;
   void SetLayerTreeHost(LayerTreeHost* host) override;
   void PushPropertiesTo(LayerImpl* layer) override;
 
   SurfaceId surface_id() const { return surface_id_; }
   const gfx::Size& surface_size() const { return surface_size_; }
   float surface_scale() const { return surface_scale_; }
 
   const SatisfyCallback& satisfy_callback() const { return satisfy_callback_; }
   const RequireCallback& require_callback() const { return require_callback_; }
 
  protected:
   SurfaceLayer(const SatisfyCallback& satisfy_callback,
                const RequireCallback& require_callback);
   bool HasDrawableContent() const override;
 
  private:
   ~SurfaceLayer() override;
   void CreateNewDestroySequence();
   void SatisfyDestroySequence();
 
   SurfaceId surface_id_;
   gfx::Size surface_size_;
-  float surface_scale_;
+  float surface_scale_ = 1.f;
+  bool stretch_content_to_fill_bounds_ = false;
   SurfaceSequence destroy_sequence_;
   SatisfyCallback satisfy_callback_;
   RequireCallback require_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceLayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_SURFACE_LAYER_H_