chromeos: Show onscreen bubble when brightness changes.

chrome/browser/chromeos/brightness_observer.h

Index: chrome/browser/chromeos/brightness_observer.h
diff --git a/chrome/browser/chromeos/brightness_observer.h b/chrome/browser/chromeos/brightness_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..ce7bc956e42f5b05b82735fea1612f39d2e9c7a3
--- /dev/null
+++ b/chrome/browser/chromeos/brightness_observer.h
@@ -0,0 +1,30 @@
+// Copyright (c) 2010 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_BRIGHTNESS_OBSERVER_H_
+#define CHROME_BROWSER_CHROMEOS_BRIGHTNESS_OBSERVER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "chrome/browser/chromeos/cros/brightness_library.h"
+
+namespace chromeos {
+
+// This observer displays a bubble at the bottom of the screen showing the
+// current brightness level whenever the user changes it.
+class BrightnessObserver : public BrightnessLibrary::Observer {
+ public:
+  BrightnessObserver() {}
+  virtual ~BrightnessObserver() {}
+
+ private:
+  // BrightnessLibrary::Observer implementation.
+  virtual void BrightnessChanged(int level);
+
+  DISALLOW_COPY_AND_ASSIGN(BrightnessObserver);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_BRIGHTNESS_OBSERVER_H_