Update from chromium https://crrev.com/302282

cc/surfaces/display.h

 // Copyright 2014 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.
 
 #ifndef CC_SURFACES_DISPLAY_H_
 #define CC_SURFACES_DISPLAY_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/output/output_surface_client.h"
 #include "cc/output/renderer.h"
@@ skipping 28 matching lines @@
                                    public RendererClient,
                                    public SurfaceDamageObserver {
  public:
   Display(DisplayClient* client,
           SurfaceManager* manager,
           SharedBitmapManager* bitmap_manager,
           gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager);
   ~Display() override;
 
   bool Initialize(scoped_ptr<OutputSurface> output_surface);
-  void Resize(SurfaceId id, const gfx::Size& new_size);
+
+  // device_scale_factor is used to communicate to the external window system
+  // what scale this was rendered at.
+  void Resize(SurfaceId id,
+              const gfx::Size& new_size,
+              float device_scale_factor);
   bool Draw();
 
   SurfaceId CurrentSurfaceId();
   int GetMaxFramesPending();
 
   // OutputSurfaceClient implementation.
   void DeferredInitialize() override {}
   void ReleaseGL() override {}
   void CommitVSyncParameters(base::TimeTicks timebase,
                              base::TimeDelta interval) override;
@@ skipping 21 matching lines @@
 
  private:
   void InitializeRenderer();
 
   DisplayClient* client_;
   SurfaceManager* manager_;
   SharedBitmapManager* bitmap_manager_;
   gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager_;
   SurfaceId current_surface_id_;
   gfx::Size current_surface_size_;
+  float device_scale_factor_;
   LayerTreeSettings settings_;
   scoped_ptr<OutputSurface> output_surface_;
   scoped_ptr<ResourceProvider> resource_provider_;
   scoped_ptr<SurfaceAggregator> aggregator_;
   scoped_ptr<DirectRenderer> renderer_;
   scoped_ptr<BlockingTaskRunner> blocking_main_thread_task_runner_;
   scoped_ptr<TextureMailboxDeleter> texture_mailbox_deleter_;
 
   DISALLOW_COPY_AND_ASSIGN(Display);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_DISPLAY_H_