Folds methods in WmShellCommon to WmShell

ash/system/chromeos/power/video_activity_notifier.cc

Index: ash/system/chromeos/power/video_activity_notifier.cc
diff --git a/ash/system/chromeos/power/video_activity_notifier.cc b/ash/system/chromeos/power/video_activity_notifier.cc
index d16004f4b71e375aa3628879b02dcb594e60a1a8..0b578f8e6bcd458b34e91a34337d94b21ced3341 100644
--- a/ash/system/chromeos/power/video_activity_notifier.cc
+++ b/ash/system/chromeos/power/video_activity_notifier.cc
@@ -19,11 +19,11 @@ const int kNotifyIntervalSec = 5;
 VideoActivityNotifier::VideoActivityNotifier(VideoDetector* detector)
     : detector_(detector), screen_is_locked_(false) {
   detector_->AddObserver(this);
-  ash::WmShell::Get()->AddShellObserver(this);
+  WmShell::Get()->AddShellObserver(this);
 }
 
 VideoActivityNotifier::~VideoActivityNotifier() {
-  ash::WmShell::Get()->RemoveShellObserver(this);
+  WmShell::Get()->RemoveShellObserver(this);
   detector_->RemoveObserver(this);
 }