Cache a screen compatible DC to avoid re-creating it excessively.

ui/gfx/screen_compatible_dc_win.h

Index: ui/gfx/screen_compatible_dc_win.h
===================================================================
--- ui/gfx/screen_compatible_dc_win.h	(revision 0)
+++ ui/gfx/screen_compatible_dc_win.h	(revision 0)
@@ -0,0 +1,32 @@
+// 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_SCREEN_COMPATIBLE_DC_WIN_H_
+#define UI_GFX_SCREEN_COMPATIBLE_DC_WIN_H_
+#pragma once
+
+#include <windows.h>
+
+#include "base/basictypes.h"
+
+namespace gfx {
+
+// Temporary device context that is compatible with the screen. Can be used for
+// short-lived operations on the UI threads.
+class ScopedTemporaryScreenCompatibleDC {
+ public:
+  ScopedTemporaryScreenCompatibleDC();
+  ~ScopedTemporaryScreenCompatibleDC();
+
+  HDC get() const { return hdc_; }
+
+ private:
+  HDC hdc_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedTemporaryScreenCompatibleDC);
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_SCREEN_COMPATIBLE_DC_WIN_H_