mash: Move SystemTrayDelegate ownership to WmShell

ash/system/chromeos/tray_tracing.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/tray_tracing.h"
 
 #include "ash/common/system/tray/fixed_sized_image_view.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/system/tray/tray_constants.h"
+#include "ash/common/wm_shell.h"
 #include "ash/shell.h"
 #include "ash/system/tray/actionable_view.h"
 #include "ash/system/tray/system_tray.h"
 #include "ash/system/tray/system_tray_notifier.h"
 #include "grit/ash_resources.h"
 #include "grit/ash_strings.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/image/image.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/controls/label.h"
@@ skipping 21 matching lines @@
     label_->SetHorizontalAlignment(gfx::ALIGN_LEFT);
     label_->SetText(bundle.GetLocalizedString(IDS_ASH_STATUS_TRAY_TRACING));
     AddChildView(label_);
   }
 
   ~DefaultTracingView() override {}
 
  private:
   // Overridden from ActionableView.
   bool PerformAction(const ui::Event& event) override {
-    Shell::GetInstance()->system_tray_delegate()->ShowChromeSlow();
+    WmShell::Get()->system_tray_delegate()->ShowChromeSlow();
     return true;
   }
 
   views::ImageView* image_;
   views::Label* label_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultTracingView);
 };
 
 }  // namespace tray
@@ skipping 38 matching lines @@
 }
 
 void TrayTracing::DestroyDetailedView() {
 }
 
 void TrayTracing::OnTracingModeChanged(bool value) {
   SetTrayIconVisible(value);
 }
 
 }  // namespace ash