mus: Forward user activity from window server to detector.

ui/chromeos/user_activity_power_manager_notifier.h

Index: ui/chromeos/user_activity_power_manager_notifier.h
diff --git a/ui/chromeos/user_activity_power_manager_notifier.h b/ui/chromeos/user_activity_power_manager_notifier.h
index 123343c5f22dc6aec97e5cb8836a731c1c559b6d..2020d377d0cc44fdbc9d2425fc8c3123a1d000b8 100644
--- a/ui/chromeos/user_activity_power_manager_notifier.h
+++ b/ui/chromeos/user_activity_power_manager_notifier.h
@@ -15,10 +15,12 @@ namespace ui {
 
 class UserActivityDetector;
 
-// Notifies the power manager when the user is active.
+// Notifies the power manager via D-Bus when the user is active.
 class UI_CHROMEOS_EXPORT UserActivityPowerManagerNotifier
     : public UserActivityObserver {
  public:
+  // Registers and unregisters itself as an observer of |detector| on
+  // construction and destruction.
   explicit UserActivityPowerManagerNotifier(UserActivityDetector* detector);
   ~UserActivityPowerManagerNotifier() override;