Views: factor out Combobox background and const-ify style

ui/gfx/scoped_canvas.h

 // Copyright 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 UI_GFX_SCOPED_CANVAS_H_
 #define UI_GFX_SCOPED_CANVAS_H_
 
 #include "base/macros.h"
 #include "ui/gfx/canvas.h"
+#include "ui/gfx/gfx_export.h"
 
 namespace gfx {
 
+class Rect;
+
 // Saves the drawing state, and restores the state when going out of scope.
-class ScopedCanvas {
+class GFX_EXPORT ScopedCanvas {
  public:
   explicit ScopedCanvas(gfx::Canvas* canvas) : canvas_(canvas) {
     if (canvas_)
       canvas_->Save();
   }
   ~ScopedCanvas() {
     if (canvas_)
       canvas_->Restore();
   }
 
  private:
   gfx::Canvas* canvas_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedCanvas);
 };
 
+// Saves the drawing state, and applies an RTL transform for the supplied rect
+// if the UI is in RTL layout. The resulting transform is such that anything
+// drawn inside the supplied rect will be flipped horizontally.
+class GFX_EXPORT ScopedRTLFlipCanvas {
+ public:
+  ScopedRTLFlipCanvas(gfx::Canvas* canvas, const gfx::Rect& rect);
+  ~ScopedRTLFlipCanvas() {}
+
+ private:
+  ScopedCanvas canvas_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedRTLFlipCanvas);
+};
+
 }  // namespace gfx
 
 #endif  // UI_GFX_SCOPED_CANVAS_H_