Refactor device scale factor on Mac and fix CoreAnimation bug

content/browser/renderer_host/render_widget_host_view_mac.h

 // Copyright (c) 2012 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 CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 #include <list>
 #include <map>
@@ skipping 461 matching lines @@
   RenderWidgetHostViewMac* fullscreen_parent_host_view() const {
     return fullscreen_parent_host_view_;
   }
 
   RenderWidgetHostViewFrameSubscriber* frame_subscriber() const {
     return frame_subscriber_.get();
   }
 
   int window_number() const;
 
-  float scale_factor() const;
+  // The scale factor for the screen that the view is currently on.
+  float ViewScaleFactor() const;
+
+  // Update the scale factor for the backing store and for any CALayers.
+  void UpdateBackingStoreScaleFactor();
+
+  // The scale factor of the backing store and all CALayers. Note that this is
+  // updated based on ViewScaleFactor with some delay.
+  float backing_store_scale_factor_;
 
   void AddPendingLatencyInfo(
       const std::vector<ui::LatencyInfo>& latency_info);
   void SendPendingLatencyInfoToHost();
   void TickPendingLatencyInfoDelay();
 
   void SendPendingSwapAck();
 
  private:
   friend class RenderWidgetHostView;
@@ skipping 110 matching lines @@
   scoped_ptr<RenderWidgetHostViewFrameSubscriber> frame_subscriber_;
 
   base::WeakPtrFactory<RenderWidgetHostViewMac>
       software_frame_weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_