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

services/ui/ws/frame_generator.cc

Index: services/ui/ws/frame_generator.cc
diff --git a/services/ui/ws/frame_generator.cc b/services/ui/ws/frame_generator.cc
index 7ca6399cf63477dec7af7271b5bebda804c8c5af..5a6f3b930d6cd2aea95e04bc6289e3e8929ae6b0 100644
--- a/services/ui/ws/frame_generator.cc
+++ b/services/ui/ws/frame_generator.cc
@@ -21,9 +21,11 @@ namespace ui {
 namespace ws {
 
 FrameGenerator::FrameGenerator(FrameGeneratorDelegate* delegate,
-                               ServerWindow* root_window)
+                               ServerWindow* root_window,
+                               float device_scale_factor)
     : delegate_(delegate),
       root_window_(root_window),
+      device_scale_factor_(device_scale_factor),
       top_level_root_surface_id_(
           cc::FrameSinkId(0, 0),
           cc::LocalFrameId(0, base::UnguessableToken::Create())),
@@ -92,6 +94,10 @@ void FrameGenerator::OnSurfaceCreated(const cc::SurfaceId& surface_id,
   ref.child_id = surface_id;
 }
 
+void FrameGenerator::UpdateDeviceScaleFactor(float device_scale_factor) {

[sky, 2016/12/03 16:28:30]

Generally for trivial functions like this we use unix_hacker_case and inline it
in the header, e.g.:
void set_device_scale_factor(...) ...

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

Done.

+  device_scale_factor_ = device_scale_factor;
+}
+
 void FrameGenerator::DidReceiveCompositorFrameAck() {}
 
 void FrameGenerator::OnBeginFrame(const cc::BeginFrameArgs& begin_frame_arags) {
@@ -155,6 +161,7 @@ cc::CompositorFrame FrameGenerator::GenerateCompositorFrame(
                  cc::FilterOperations() /* background_filters */);
     frame.render_pass_list.push_back(std::move(invert_pass));
   }
+  frame.metadata.device_scale_factor = device_scale_factor_;
 
   return frame;
 }