Pass accurate contentsScale to LayerImpl.

cc/contents_scaling_layer.h

Index: cc/contents_scaling_layer.h
diff --git a/cc/contents_scaling_layer.h b/cc/contents_scaling_layer.h
new file mode 100644
index 0000000000000000000000000000000000000000..3151a303cd09570a6d332a9dfda8b0aa54b10eb6
--- /dev/null
+++ b/cc/contents_scaling_layer.h
@@ -0,0 +1,30 @@
+// 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_CONTENTS_SCALING_LAYER_H
+#define CC_CONTENTS_SCALING_LAYER_H
+
+#include "cc/layer.h"
+
+namespace cc {
+
+// Base class for layers that need contents scale.
+// The content bounds are determined by bounds and scale of the contents.
+class ContentsScalingLayer : public Layer {
+ public:
+  ContentsScalingLayer();
+  virtual ~ContentsScalingLayer();
+
+  virtual IntSize contentBounds() const OVERRIDE;
+  virtual float contentsScaleX() const OVERRIDE { return m_contentsScale; }
+  virtual float contentsScaleY() const OVERRIDE { return m_contentsScale; }
+  virtual void setContentsScale(float contentsScale) OVERRIDE;
+
+ private:
+  float m_contentsScale;
+};
+
+}  // namespace cc
+
+#endif  // CC_CONTENTS_SCALING_LAYER_H