Move yet more from WmShell to Shell

ash/system/chromeos/power/tablet_power_button_controller.cc

 // Copyright 2016 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/tablet_power_button_controller.h"
 
 #include "ash/common/accessibility_delegate.h"
 #include "ash/common/session/session_controller.h"
 #include "ash/common/shell_delegate.h"
 #include "ash/common/wm/maximize_mode/maximize_mode_controller.h"
@@ skipping 234 matching lines @@
                                          : kShutdownWhenScreenOnTimeoutMs);
   shutdown_timer_.Start(FROM_HERE, timeout, this,
                         &TabletPowerButtonController::OnShutdownTimeout);
 }
 
 void TabletPowerButtonController::OnShutdownTimeout() {
   controller_->StartShutdownAnimation();
 }
 
 void TabletPowerButtonController::LockScreenIfRequired() {
-  SessionController* session_controller = WmShell::Get()->session_controller();
+  SessionController* session_controller = Shell::Get()->session_controller();
   if (session_controller->ShouldLockScreenAutomatically() &&
       session_controller->CanLockScreen() &&
       !session_controller->IsUserSessionBlocked() &&
       !controller_->LockRequested()) {
     session_controller->LockScreen();
   }
 }
 
 }  // namespace ash