Save display preference when all display configuration changes has been completed.

chrome/browser/chromeos/display/display_configuration_observer.h

Index: chrome/browser/chromeos/display/display_configuration_observer.h
diff --git a/chrome/browser/chromeos/display/display_configuration_observer.h b/chrome/browser/chromeos/display/display_configuration_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..f5d0908e94c6ff042b17384de3fc001c19376ae8
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+++ b/chrome/browser/chromeos/display/display_configuration_observer.h
@@ -0,0 +1,31 @@
+// Copyright (c) 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 CHROME_BROWSER_CHROMEOS_DISPLAY_DISPLAY_CONFIGURATION_OBSERVER_H_
+#define CHROME_BROWSER_CHROMEOS_DISPLAY_DISPLAY_CONFIGURATION_OBSERVER_H_
+
+#include "ash/display/display_controller.h"
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+
+namespace chromeos {
+
+// DisplayConfigurationObserver observes and saves
+// the change of display configurations.
+class DisplayConfigurationObserver : public ash::DisplayController::Observer {
+ public:
+  DisplayConfigurationObserver();
+  virtual ~DisplayConfigurationObserver();
+
+ protected:
+  // ash::DisplayController::Observer overrides:
+  virtual void OnDisplayConfigurationChanging() OVERRIDE;
+  virtual void OnDisplayConfigurationChanged() OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(DisplayConfigurationObserver);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_DISPLAY_DISPLAY_CONFIGURATION_OBSERVER_H_