Moves maintaining ShellObservers back to Shell

ash/system/chromeos/power/video_activity_notifier.cc

 // Copyright 2013 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.
 
 #include "ash/system/chromeos/power/video_activity_notifier.h"
 
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/wm_shell.h"
 #include "ash/shell.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/power_manager_client.h"
 
 namespace ash {
 namespace {
 
 // Minimum number of seconds between repeated notifications of the same state.
 // This should be less than powerd's timeout for determining whether video is
 // still active for the purposes of controlling the keyboard backlight.
 const int kNotifyIntervalSec = 5;
 
 }  // namespace
 
 VideoActivityNotifier::VideoActivityNotifier(VideoDetector* detector)
     : detector_(detector),
       video_state_(detector->state()),
       screen_is_locked_(
           Shell::GetInstance()->session_state_delegate()->IsScreenLocked()) {
   detector_->AddObserver(this);
-  WmShell::Get()->AddShellObserver(this);
+  Shell::GetInstance()->AddShellObserver(this);
 
   MaybeNotifyPowerManager();
   UpdateTimer();
 }
 
 VideoActivityNotifier::~VideoActivityNotifier() {
-  WmShell::Get()->RemoveShellObserver(this);
+  Shell::GetInstance()->RemoveShellObserver(this);
   detector_->RemoveObserver(this);
 }
 
 void VideoActivityNotifier::OnVideoStateChanged(VideoDetector::State state) {
   if (video_state_ != state) {
     video_state_ = state;
     MaybeNotifyPowerManager();
     UpdateTimer();
   }
 }
@@ skipping 27 matching lines @@
 void VideoActivityNotifier::MaybeNotifyPowerManager() {
   if (should_notify_power_manager()) {
     chromeos::DBusThreadManager::Get()
         ->GetPowerManagerClient()
         ->NotifyVideoActivity(video_state_ ==
                               VideoDetector::State::PLAYING_FULLSCREEN);
   }
 }
 
 }  // namespace ash