GetScaleFactorForNativeView should return scale factor in float

chrome/browser/thumbnails/thumbnailing_algorithm.h

 // Copyright (c) 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 CHROME_BROWSER_THUMBNAILS_THUMBNAILING_ALGORITHM_H_
 #define CHROME_BROWSER_THUMBNAILS_THUMBNAILING_ALGORITHM_H_
 
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/thumbnails/thumbnailing_context.h"
+#include "ui/base/layout.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 
 class SkBitmap;
 
 namespace thumbnails {
 
 // An interface abstracting thumbnailing algorithms. Instances are intended to
 // be created by ThumbnailService's implementations and used by
 // ThumbnailTabHelper as consumers of captured source images.
@@ skipping 26 matching lines @@
                              const SkBitmap& bitmap) = 0;
 
  protected:
   virtual ~ThumbnailingAlgorithm() {}
   friend class base::RefCountedThreadSafe<ThumbnailingAlgorithm>;
 };
 
 }
 
 #endif  // CHROME_BROWSER_THUMBNAILS_THUMBNAILING_ALGORITHM_H_