Pass accurate contentsScale to LayerImpl.

cc/layer.h

Index: cc/layer.h
diff --git a/cc/layer.h b/cc/layer.h
index 38a32dd845ff9cbf02315518e9d18434ac1d8866..aa791689b5357d899da44d2cfb84c6dfc999a4bf 100644
--- a/cc/layer.h
+++ b/cc/layer.h
@@ -189,7 +189,6 @@ public:
     virtual bool needMoreUpdates();
     virtual void setIsMask(bool) { }
     virtual void bindContentsTexture() { }
-    virtual bool needsContentsScale() const;
 
     void setDebugBorderColor(SkColor);
     void setDebugBorderWidth(float);
@@ -229,8 +228,10 @@ public:
 
     // The contentsScale converts from logical, non-page-scaled pixels to target pixels.
     // The contentsScale is 1 for the root layer as it is already in physical pixels.
-    float contentsScale() const { return m_contentsScale; }
-    void setContentsScale(float);
+    // By default contentsScale is forced to be 1 except for subclasses of ContentsScalingLayer.
+    virtual float contentsScaleX() const { return 1.0; }
+    virtual float contentsScaleY() const { return 1.0; }
+    virtual void setContentsScale(float contentsScale) { }
 
     // The scale at which contents should be rastered, to match the scale at
     // which they will drawn to the screen. This scale is a component of the
@@ -390,7 +391,6 @@ private:
 
     // Uses target surface space.
     IntRect m_drawableContentRect;
-    float m_contentsScale;
     float m_rasterScale;
     bool m_automaticallyComputeRasterScale;
     bool m_boundsContainPageScale;