change backing store cache to be memory-based rather than count

base/gfx/size.h

 // Copyright (c) 2006-2008 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 BASE_GFX_SIZE_H_
 #define BASE_GFX_SIZE_H_
 
 #include "build/build_config.h"
 
 #include <iostream>
@@ skipping 12 matching lines @@
 class Size {
  public:
   Size() : width_(0), height_(0) {}
   Size(int width, int height);
 
   ~Size() {}
 
   int width() const { return width_; }
   int height() const { return height_; }
 
+  int GetArea() const { return width_ * height_; }
+
   void SetSize(int width, int height) {
     set_width(width);
     set_height(height);
   }
 
   void Enlarge(int width, int height) {
     set_width(width_ + width);
     set_height(height_ + height);
   }
 
@@ skipping 24 matching lines @@
   int height_;
 };
 
 }  // namespace gfx
 
 inline std::ostream& operator<<(std::ostream& out, const gfx::Size& s) {
   return out << s.width() << "x" << s.height();
 }
 
 #endif  // BASE_GFX_SIZE_H_