Part 1/3 (compositor) of adding with device scale factor to transport surfaces

cc/output/renderer.h

Index: cc/output/renderer.h
diff --git a/cc/output/renderer.h b/cc/output/renderer.h
index b1b9f4844266e0726504578f145b9905b16eaa2c..5592090771f68784141fd962718fa38f2962b03d 100644
--- a/cc/output/renderer.h
+++ b/cc/output/renderer.h
@@ -21,6 +21,7 @@ class ScopedResource;
 class CC_EXPORT RendererClient {
  public:
   virtual gfx::Size DeviceViewportSize() const = 0;
+  virtual float DeviceScaleFactor() const = 0;
   virtual const LayerTreeSettings& Settings() const = 0;
   virtual void SetFullRootLayerDamage() = 0;
   virtual void SetManagedMemoryPolicy(const ManagedMemoryPolicy& policy) = 0;
@@ -47,6 +48,8 @@ class CC_EXPORT Renderer {
   int ViewportWidth() const { return ViewportSize().width(); }
   int ViewportHeight() const { return ViewportSize().height(); }
 
+  float DeviceScaleFactor() const { return client_->DeviceScaleFactor(); }
+
   virtual void ViewportChanged() {}
   virtual void ReceiveCompositorFrameAck(const CompositorFrameAck& ack) {}