Efficiently handle image layer scaling

cc/picture_image_layer_impl.h

+// Copyright 2013 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_PICTURE_IMAGE_LAYER_IMPL_H_
+#define CC_PICTURE_IMAGE_LAYER_IMPL_H_
+
+#include "cc/picture_layer_impl.h"
+
+namespace cc {
+
+class CC_EXPORT PictureImageLayerImpl : public PictureLayerImpl {
+ public:
+  static scoped_ptr<PictureImageLayerImpl> create(LayerTreeImpl* treeImpl,
+                                                  int id) {
+    return make_scoped_ptr(new PictureImageLayerImpl(treeImpl, id));
+  }
+  virtual ~PictureImageLayerImpl();
+
+  virtual const char* layerTypeAsString() const OVERRIDE;
+  virtual scoped_ptr<LayerImpl> createLayerImpl(
+      LayerTreeImpl* treeImpl) OVERRIDE;
+
+ protected:
+  PictureImageLayerImpl(LayerTreeImpl* treeImpl, int id);
+
+  virtual void CalculateRasterContentsScale(
+      bool animating_transform_to_screen,
+      float* raster_contents_scale,
+      float* low_res_raster_contents_scale) OVERRIDE;
+  virtual void getDebugBorderProperties(
+      SkColor* color, float* width) const OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(PictureImageLayerImpl);
+};
+
+}
+
+#endif  // CC_PICTURE_IMAGE_LAYER_IMPL_H_