mash: Move SystemTrayDelegate ownership to WmShell

ash/system/tray_update.cc

Index: ash/system/tray_update.cc
diff --git a/ash/system/tray_update.cc b/ash/system/tray_update.cc
index befe8709be12929a9492b9750f9b8e00f18e4ae4..ac46d50fb29be1c15c2a2bb2fec5a26da03cba7e 100644
--- a/ash/system/tray_update.cc
+++ b/ash/system/tray_update.cc
@@ -7,6 +7,7 @@
 #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/system_tray.h"
 #include "ash/system/tray/system_tray_notifier.h"
@@ -75,8 +76,7 @@ class UpdateView : public ash::ActionableView {
  private:
   // Overridden from ActionableView.
   bool PerformAction(const ui::Event& event) override {
-    ash::Shell::GetInstance()->
-        system_tray_delegate()->RequestRestartForUpdate();
+    ash::WmShell::Get()->system_tray_delegate()->RequestRestartForUpdate();
     return true;
   }
 
@@ -98,13 +98,13 @@ TrayUpdate::~TrayUpdate() {
 
 bool TrayUpdate::GetInitialVisibility() {
   UpdateInfo info;
-  Shell::GetInstance()->system_tray_delegate()->GetSystemUpdateInfo(&info);
+  WmShell::Get()->system_tray_delegate()->GetSystemUpdateInfo(&info);
   return info.update_required;
 }
 
 views::View* TrayUpdate::CreateDefaultView(LoginStatus status) {
   UpdateInfo info;
-  Shell::GetInstance()->system_tray_delegate()->GetSystemUpdateInfo(&info);
+  WmShell::Get()->system_tray_delegate()->GetSystemUpdateInfo(&info);
   return info.update_required ? new UpdateView(info) : nullptr;
 }