Add OVERRIDE to chrome/browser/chromeos/.

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
index d8f5b6630e05d7c2f57662a18d7705b6f4cfa7dc..b18a9a516842255fde293310242f44ea5e4d3401 100644
--- a/chrome/browser/chromeos/brightness_observer.h
+++ b/chrome/browser/chromeos/brightness_observer.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include "base/basictypes.h"
+#include "base/compiler_specific.h"
 #include "chrome/browser/chromeos/dbus/power_manager_client.h"
 
 namespace chromeos {
@@ -20,7 +21,7 @@ class BrightnessObserver : public PowerManagerClient::Observer {
 
  private:
   // PowerManagerClient::Observer implementation.
-  virtual void BrightnessChanged(int level, bool user_initiated);
+  virtual void BrightnessChanged(int level, bool user_initiated) OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(BrightnessObserver);
 };