Fix Aura backing store to work with non-integer scale factors.

content/browser/renderer_host/backing_store_aura.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_AURA_H_
 #define CONTENT_BROWSER_RENDERER_HOST_BACKING_STORE_AURA_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "content/browser/renderer_host/backing_store.h"
 #include "content/common/content_export.h"
@@ skipping 38 matching lines @@
   virtual bool CopyFromBackingStore(const gfx::Rect& rect,
                                     skia::PlatformBitmap* output) OVERRIDE;
   virtual void ScrollBackingStore(const gfx::Vector2d& delta,
                                   const gfx::Rect& clip_rect,
                                   const gfx::Size& view_size) OVERRIDE;
 
  private:
   SkBitmap bitmap_;
 
   scoped_ptr<SkCanvas> canvas_;
-  int device_scale_factor_;
+  float device_scale_factor_;
 
   DISALLOW_COPY_AND_ASSIGN(BackingStoreAura);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_BACKING_STORE_AURA_H_