Makes Background only create a brush when needed. This avoids

views/background.h

 // Copyright (c) 2009 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 VIEWS_BACKGROUND_H_
 #define VIEWS_BACKGROUND_H_
 #pragma once
 
 #include "build/build_config.h"
 
@@ skipping 66 matching lines @@
   // Returns the "background color".  This is equivalent to the color set in
   // SetNativeControlColor().  For solid backgrounds, this is the color; for
   // gradient backgrounds, it's the midpoint of the gradient; for painter
   // backgrounds, this is not useful (returns a default color).
   SkColor get_color() const { return color_; }
 
 #if defined(OS_WIN)
   // TODO(port): Make GetNativeControlBrush portable (currently uses HBRUSH).
 
   // Get the brush that was specified by SetNativeControlColor
-  HBRUSH GetNativeControlBrush() const { return native_control_brush_; };
+  HBRUSH GetNativeControlBrush() const;
 #endif  // defined(OS_WIN)
 
  private:
   SkColor color_;
 #if defined(OS_WIN)
   // TODO(port): Create portable replacement for HBRUSH.
-  HBRUSH native_control_brush_;
+  mutable HBRUSH native_control_brush_;
 #endif  // defined(OS_WIN)
 
   DISALLOW_COPY_AND_ASSIGN(Background);
 };
 
 }  // namespace views
 
 #endif  // VIEWS_BACKGROUND_H_