gfx: Make conversions from Size to SizeF be explicit.

chrome/browser/android/thumbnail/thumbnail.h

 // Copyright 2014 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_ANDROID_THUMBNAIL_THUMBNAIL_H_
 #define CHROME_BROWSER_ANDROID_THUMBNAIL_THUMBNAIL_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "cc/resources/ui_resource_bitmap.h"
 #include "cc/resources/ui_resource_client.h"
 #include "ui/android/resources/ui_resource_client_android.h"
-#include "ui/gfx/geometry/size.h"
+#include "ui/gfx/geometry/size_f.h"
 
 namespace base {
 class Time;
 }
 
 namespace gfx {
 class Size;
 }
 
 namespace ui {
@@ skipping 60 matching lines @@
 
   bool retrieved_;
 
   ui::UIResourceProvider* ui_resource_provider_;
   ThumbnailDelegate* thumbnail_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(Thumbnail);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_THUMBNAIL_THUMBNAIL_H_