Refactor device scale factor on Mac and fix CoreAnimation bug

content/browser/renderer_host/compositing_iosurface_layer_mac.h

 // Copyright 2013 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_COMPOSITING_IOSURFACE_LAYER_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_LAYER_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/scoped_cftyperef.h"
@@ skipping 14 matching lines @@
   // in response to receiving a new compositor frame, or from any of the events
   // that cause setNeedsDisplay to be called on the layer.
   BOOL needsDisplay_;
 }
 
 @property(nonatomic, readonly)
     scoped_refptr<content::CompositingIOSurfaceContext> context;
 
 - (id)initWithRenderWidgetHostViewMac:(content::RenderWidgetHostViewMac*)r;
 
-// Update the scale factor of the layer to match the scale factor of the
-// IOSurface.
-- (void)updateScaleFactor;
-
 // Remove this layer from the layer heirarchy, and mark that
 // |renderWidgetHostView_| is no longer valid and may no longer be dereferenced.
 - (void)disableCompositing;
 
 // Called when a new frame is received.
 - (void)gotNewFrame;
 
 // Called when it has been a while since a new frame has been received, and the
 // layer should become not-asynchronous.
 - (void)timerSinceGotNewFrameFired;
 
 @end
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_COMPOSITING_IOSURFACE_LAYER_MAC_H_