Make adding and subtracting gfx:: point types simpler.

ui/gfx/size.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 UI_GFX_SIZE_H_
 #define UI_GFX_SIZE_H_
 
 #include <string>
 
 #include "build/build_config.h"
 #include "ui/base/ui_export.h"
 #include "ui/gfx/size_base.h"
+#include "ui/gfx/size_f.h"
 
 #if defined(OS_WIN)
 typedef struct tagSIZE SIZE;
 #elif defined(OS_IOS)
 #include <CoreGraphics/CoreGraphics.h>
 #elif defined(OS_MACOSX)
 #include <ApplicationServices/ApplicationServices.h>
 #endif
 
 namespace gfx {
@@ skipping 12 matching lines @@
 #if defined(OS_MACOSX)
   Size& operator=(const CGSize& s);
 #endif
 
 #if defined(OS_WIN)
   SIZE ToSIZE() const;
 #elif defined(OS_MACOSX)
   CGSize ToCGSize() const;
 #endif
 
+  SizeF ToSizeF() const {
+    return SizeF(width(), height());
+  }
+
   std::string ToString() const;
 };
 
 #if !defined(COMPILER_MSVC)
 extern template class SizeBase<Size, int>;
 #endif
 
 }  // namespace gfx
 
 #endif  // UI_GFX_SIZE_H_