chromeos: Add support for dimming the screen.

chrome/browser/chromeos/power/screen_dimming_observer.cc

+// 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.
+
+#include "chrome/browser/chromeos/power/screen_dimming_observer.h"
+
+#include "ash/shell.h"
+#include "ash/wm/screen_dimmer.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+
+namespace chromeos {
+
+ScreenDimmingObserver::ScreenDimmingObserver() {
+  DBusThreadManager::Get()->GetPowerManagerClient()->AddObserver(this);
+}
+
+ScreenDimmingObserver::~ScreenDimmingObserver() {
+  DBusThreadManager::Get()->GetPowerManagerClient()->RemoveObserver(this);
+}
+
+void ScreenDimmingObserver::ScreenDimmingRequested(ScreenDimmingState state) {
+  ash::Shell::GetInstance()->screen_dimmer()->SetDimming(
+      state == PowerManagerClient::Observer::SCREEN_DIMMING_IDLE);
+}
+
+}  // namespace chromeos