mac: Make dynamic DPI changes work.

content/browser/renderer_host/backing_store_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_BACKING_STORE_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_BACKING_STORE_MAC_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "content/browser/renderer_host/backing_store.h"
 
 class BackingStoreMac : public BackingStore {
  public:
   // |size| is in view units, |device_scale_factor| is the backingScaleFactor.
   // The pixel size of the backing store is size.Scale(device_scale_factor).
   BackingStoreMac(content::RenderWidgetHost* widget,
                   const gfx::Size& size,
                   float device_scale_factor);
   virtual ~BackingStoreMac();
 
   // A CGLayer that stores the contents of the backing store, cached in GPU
   // memory if possible.
   CGLayerRef cg_layer() { return cg_layer_; }
 
   // A CGBitmapContext that stores the contents of the backing store if the
   // corresponding Cocoa view has not been inserted into an NSWindow yet.
   CGContextRef cg_bitmap() { return cg_bitmap_; }
 
+  void ScaleFactorChanged(float device_scale_factor);
+
   // BackingStore implementation.
   virtual size_t MemorySize() OVERRIDE;
   virtual void PaintToBackingStore(
       content::RenderProcessHost* process,
       TransportDIB::Id bitmap,
       const gfx::Rect& bitmap_rect,
       const std::vector<gfx::Rect>& copy_rects,
       float scale_factor,
       const base::Closure& completion_callback,
       bool* scheduled_completion_callback) OVERRIDE;
@@ skipping 21 matching lines @@
   base::mac::ScopedCFTypeRef<CGContextRef> cg_bitmap_;
   base::mac::ScopedCFTypeRef<CGLayerRef> cg_layer_;
 
   // Number of physical pixels per view unit. This is 1 or 2 in practice.
   float device_scale_factor_;
 
   DISALLOW_COPY_AND_ASSIGN(BackingStoreMac);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_BACKING_STORE_MAC_H_