Set device scale factor in CompositorFrame and scale frame size in WS.

services/ui/ws/frame_generator.h

Index: services/ui/ws/frame_generator.h
diff --git a/services/ui/ws/frame_generator.h b/services/ui/ws/frame_generator.h
index c93e1220826edcaf3a49b64ad34c10ae9980409c..6de5770dd4b0a2703a86f7ea4ce57dbf906c03f6 100644
--- a/services/ui/ws/frame_generator.h
+++ b/services/ui/ws/frame_generator.h
@@ -49,7 +49,9 @@ class ServerWindow;
 class FrameGenerator : public ServerWindowTracker,
                        public cc::mojom::MojoCompositorFrameSinkClient {
  public:
-  FrameGenerator(FrameGeneratorDelegate* delegate, ServerWindow* root_window);
+  FrameGenerator(FrameGeneratorDelegate* delegate,
+                 ServerWindow* root_window,
+                 float device_scale_factor);

[kylechar, 2016/12/05 14:46:11]

Instead of adding another parameter to the constructor, you could just call
frame_generator_.set_device_scale_factor(...) after the constructor?

[riajiang, 2016/12/09 19:31:44]

Done.

   ~FrameGenerator() override;
 
   // Schedules a redraw for the provided region.
@@ -70,6 +72,8 @@ class FrameGenerator : public ServerWindowTracker,
   // CompositorFrame is submitted.
   void OnSurfaceCreated(const cc::SurfaceId& surface_id, ServerWindow* window);
 
+  void UpdateDeviceScaleFactor(float device_scale_factor);
+
  private:
   friend class ui::ws::test::FrameGeneratorTest;
 
@@ -120,6 +124,7 @@ class FrameGenerator : public ServerWindowTracker,
 
   FrameGeneratorDelegate* delegate_;
   ServerWindow* const root_window_;
+  float device_scale_factor_;
 
   gfx::Size last_submitted_frame_size_;
   cc::LocalFrameId local_frame_id_;