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

services/ui/surfaces/display_compositor.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "services/ui/surfaces/display_compositor.h"
 
 #include <utility>
 
 #include "cc/output/in_process_context_provider.h"
 #include "cc/output/texture_mailbox_deleter.h"
@@ skipping 208 matching lines @@
 }
 
 const cc::SurfaceId& DisplayCompositor::GetRootSurfaceId() const {
   return reference_manager_->GetRootSurfaceId();
 }
 
 void DisplayCompositor::OnSurfaceCreated(const cc::SurfaceId& surface_id,
                                          const gfx::Size& frame_size,
                                          float device_scale_factor) {
   DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(device_scale_factor);

[kylechar, 2016/12/15 18:25:03]

DCHECK_GT(device_scale_factor, 0.0f) maybe so it's clear it's a float?

[riajiang, 2016/12/15 19:01:43]

Done.

   // We can get into a situation where multiple CompositorFrames arrive for a
   // CompositorFrameSink before the DisplayCompositorClient can add any
   // references for the frame. When the second frame with a new size arrives,
   // the first will be destroyed and then if there are no references it will be
   // deleted during surface GC. A temporary reference, removed when a real
   // reference is received, is added to prevent this from happening.
   reference_manager_->AddSurfaceReference(GetRootSurfaceId(), surface_id);
   temp_references_[surface_id.frame_sink_id()].push_back(
       surface_id.local_frame_id());
 
   if (client_)
     client_->OnSurfaceCreated(surface_id, frame_size, device_scale_factor);
 }
 
 void DisplayCompositor::OnSurfaceDamaged(const cc::SurfaceId& surface_id,
                                          bool* changed) {}
 
 }  // namespace ui