Migrate simple ash Shell metrics users.

ash/system/overview/overview_button_tray.cc

 // Copyright 2014 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/overview/overview_button_tray.h"
 
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/shelf_types.h"
@@ skipping 39 matching lines @@
   } else {
     gfx::ImageSkia* image_non_md =
         ui::ResourceBundle::GetSharedInstance().GetImageSkiaNamed(
             IDR_AURA_UBER_TRAY_OVERVIEW_MODE);
     icon_->SetImage(image_non_md);
   }
   SetIconBorderForShelfAlignment();
   tray_container()->AddChildView(icon_);
 
   WmShell::Get()->AddShellObserver(this);
-  Shell::GetInstance()->session_state_delegate()->AddSessionStateObserver(this);
+  WmShell::Get()->GetSessionStateDelegate()->AddSessionStateObserver(this);
 }
 
 OverviewButtonTray::~OverviewButtonTray() {
   WmShell::Get()->RemoveShellObserver(this);
-  Shell::GetInstance()->session_state_delegate()->RemoveSessionStateObserver(
-      this);
+  WmShell::Get()->GetSessionStateDelegate()->RemoveSessionStateObserver(this);
 }
 
 void OverviewButtonTray::UpdateAfterLoginStatusChange(LoginStatus status) {
   UpdateIconVisibility();
 }
 
 bool OverviewButtonTray::PerformAction(const ui::Event& event) {
   WindowSelectorController* controller =
       WmShell::Get()->window_selector_controller();
   controller->ToggleOverview();
   SetDrawBackgroundAsActive(controller->IsSelecting());
-  Shell::GetInstance()->metrics()->RecordUserMetricsAction(UMA_TRAY_OVERVIEW);
+  WmShell::Get()->RecordUserMetricsAction(UMA_TRAY_OVERVIEW);
   return true;
 }
 
 void OverviewButtonTray::SessionStateChanged(
     SessionStateDelegate::SessionState state) {
   UpdateIconVisibility();
 }
 
 void OverviewButtonTray::OnMaximizeModeStarted() {
   UpdateIconVisibility();
@@ skipping 42 matching lines @@
   }
 }
 
 void OverviewButtonTray::UpdateIconVisibility() {
   // The visibility of the OverviewButtonTray has diverge from
   // WindowSelectorController::CanSelect. The visibility of the button should
   // not change during transient times in which CanSelect is false. Such as when
   // a modal dialog is present.
   Shell* shell = Shell::GetInstance();
   SessionStateDelegate* session_state_delegate =
-      shell->session_state_delegate();
+      WmShell::Get()->GetSessionStateDelegate();
 
   SetVisible(
       shell->maximize_mode_controller()->IsMaximizeModeWindowManagerEnabled() &&
       session_state_delegate->IsActiveUserSessionStarted() &&
       !session_state_delegate->IsScreenLocked() &&
       session_state_delegate->GetSessionState() ==
           SessionStateDelegate::SESSION_STATE_ACTIVE &&
       WmShell::Get()->system_tray_delegate()->GetUserLoginStatus() !=
           LoginStatus::KIOSK_APP);
 }
 
 }  // namespace ash