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

content/browser/compositor/mus_browser_compositor_output_surface.h

Index: content/browser/compositor/mus_browser_compositor_output_surface.h
diff --git a/content/browser/compositor/mus_browser_compositor_output_surface.h b/content/browser/compositor/mus_browser_compositor_output_surface.h
index 476f4524b86dedb482f11f8b28df57f6dbe50a59..c7b375d04d3901591226b3697dfa915c303dd007 100644
--- a/content/browser/compositor/mus_browser_compositor_output_surface.h
+++ b/content/browser/compositor/mus_browser_compositor_output_surface.h
@@ -47,7 +47,8 @@ class MusBrowserCompositorOutputSurface
       scoped_refptr<ui::CompositorVSyncManager> vsync_manager,
       cc::SyntheticBeginFrameSource* begin_frame_source,
       std::unique_ptr<display_compositor::CompositorOverlayCandidateValidator>
-          overlay_candidate_validator);
+          overlay_candidate_validator,
+      float device_scale_factor);
 
   MusBrowserCompositorOutputSurface(
       aura::Window* window,
@@ -56,7 +57,8 @@ class MusBrowserCompositorOutputSurface
       scoped_refptr<ui::CompositorVSyncManager> vsync_manager,
       cc::SyntheticBeginFrameSource* begin_frame_source,
       std::unique_ptr<display_compositor::CompositorOverlayCandidateValidator>
-          overlay_candidate_validator);
+          overlay_candidate_validator,
+      float device_scale_factor);
 
   ~MusBrowserCompositorOutputSurface() override;
 
@@ -89,6 +91,7 @@ class MusBrowserCompositorOutputSurface
 
   aura::Window* window_;
   std::unique_ptr<aura::WindowCompositorFrameSink> compositor_frame_sink_;
+  float device_scale_factor_;
   std::vector<uint32_t> free_resource_ids_;
   std::vector<gpu::Mailbox> mailboxes_;