chromeos: Add support for dimming the screen.

chrome/browser/chromeos/power/screen_dimming_observer.h

+// 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 CHROME_BROWSER_CHROMEOS_POWER_SCREEN_DIMMING_OBSERVER_H_
+#define CHROME_BROWSER_CHROMEOS_POWER_SCREEN_DIMMING_OBSERVER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "chromeos/dbus/power_manager_client.h"
+
+namespace chromeos {
+
+// Listens for requests to enable or disable dimming of the screen in software
+// (as opposed to by adjusting a backlight).
+class ScreenDimmingObserver : public PowerManagerClient::Observer {
+ public:
+  // This class registers/unregisters itself as an observer in ctor/dtor.
+  ScreenDimmingObserver();
+  virtual ~ScreenDimmingObserver();
+
+ private:
+  // PowerManagerClient::Observer implementation.
+  virtual void ScreenDimmingRequested(ScreenDimmingState state) OVERRIDE;
+
+  DISALLOW_COPY_AND_ASSIGN(ScreenDimmingObserver);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_POWER_SCREEN_DIMMING_OBSERVER_H_