chromeos: Ignore power button presses when screen is off.

chrome/browser/chromeos/power/brightness_observer.cc

Index: chrome/browser/chromeos/power/brightness_observer.cc
diff --git a/chrome/browser/chromeos/power/brightness_observer.cc b/chrome/browser/chromeos/power/brightness_observer.cc
index cd4e4a5879d523262a6b78ff083ae62e376de203..cbf511961bb5fc97eec220cbd61f019231a700b9 100644
--- a/chrome/browser/chromeos/power/brightness_observer.cc
+++ b/chrome/browser/chromeos/power/brightness_observer.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/chromeos/power/brightness_observer.h"
 
+#include "ash/shell.h"
+#include "ash/wm/power_button_controller.h"
 #include "chrome/browser/extensions/system/system_api.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 
@@ -19,6 +21,8 @@ BrightnessObserver::~BrightnessObserver() {
 
 void BrightnessObserver::BrightnessChanged(int level, bool user_initiated) {
   extensions::DispatchBrightnessChangedEvent(level, user_initiated);
+  ash::Shell::GetInstance()->power_button_controller()->
+      OnScreenBrightnessChanged(static_cast<double>(level));
 }
 
 }  // namespace chromeos