Moves maintaining ShellObservers back to Shell

ash/common/system/chromeos/screen_security/screen_capture_tray_item.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/common/system/chromeos/screen_security/screen_capture_tray_item.h"
 
 #include <utility>
 
 #include "ash/common/metrics/user_metrics_action.h"
 #include "ash/common/system/system_notifier.h"
 #include "ash/common/system/tray/system_tray_notifier.h"
 #include "ash/common/wm_shell.h"
 #include "ash/resources/grit/ash_resources.h"
+#include "ash/shell.h"
 #include "ash/strings/grit/ash_strings.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/message_center/message_center.h"
 #include "ui/message_center/notification.h"
 
 using message_center::Notification;
 
 namespace ash {
 namespace {
 
 const char kScreenCaptureNotificationId[] = "chrome://screen/capture";
 
 }  // namespace
 
 ScreenCaptureTrayItem::ScreenCaptureTrayItem(SystemTray* system_tray)
     : ScreenTrayItem(system_tray, UMA_SCREEN_CAPTURE) {
-  WmShell::Get()->AddShellObserver(this);
+  Shell::GetInstance()->AddShellObserver(this);
   WmShell::Get()->system_tray_notifier()->AddScreenCaptureObserver(this);
 }
 
 ScreenCaptureTrayItem::~ScreenCaptureTrayItem() {
-  WmShell::Get()->RemoveShellObserver(this);
+  Shell::GetInstance()->RemoveShellObserver(this);
   WmShell::Get()->system_tray_notifier()->RemoveScreenCaptureObserver(this);
 }
 
 views::View* ScreenCaptureTrayItem::CreateDefaultView(LoginStatus status) {
   set_default_view(new tray::ScreenStatusView(
       this, screen_capture_status_,
       l10n_util::GetStringUTF16(IDS_ASH_STATUS_TRAY_SCREEN_CAPTURE_STOP)));
   return default_view();
 }
 
@@ skipping 52 matching lines @@
   // screen capture is stopped externally.
   set_is_started(false);
   Update();
 }
 
 void ScreenCaptureTrayItem::OnCastingSessionStartedOrStopped(bool started) {
   is_casting_ = started;
 }
 
 }  // namespace ash