mash: Move SystemTrayDelegate ownership to WmShell

ash/system/chromeos/tray_display_unittest.cc

Index: ash/system/chromeos/tray_display_unittest.cc
diff --git a/ash/system/chromeos/tray_display_unittest.cc b/ash/system/chromeos/tray_display_unittest.cc
index 306611d2a27d58e72b1f2669c471fbfab06cb2ae..2f2eda47405d546760780d6357d422007540cc84 100644
--- a/ash/system/chromeos/tray_display_unittest.cc
+++ b/ash/system/chromeos/tray_display_unittest.cc
@@ -4,6 +4,7 @@
 
 #include "ash/system/chromeos/tray_display.h"
 
+#include "ash/common/wm_shell.h"
 #include "ash/display/display_manager.h"
 #include "ash/root_window_controller.h"
 #include "ash/screen_util.h"
@@ -445,7 +446,7 @@ TEST_F(TrayDisplayTest, UpdateDuringDisplayConfigurationChange) {
 TEST_F(TrayDisplayTest, DisplayNotifications) {
   test::TestSystemTrayDelegate* tray_delegate =

[msw, 2016/06/10 18:48:21]

nit: AshTestBase::GetSystemTrayDelegate here and twice more below.

[James Cook, 2016/06/10 20:20:32]

Done.

       static_cast<test::TestSystemTrayDelegate*>(
-          Shell::GetInstance()->system_tray_delegate());
+          WmShell::Get()->system_tray_delegate());
   tray_delegate->set_should_show_display_notification(true);
 
   UpdateDisplay("400x400");
@@ -556,7 +557,7 @@ TEST_F(TrayDisplayTest, DisplayNotifications) {
 TEST_F(TrayDisplayTest, DisplayConfigurationChangedTwice) {
   test::TestSystemTrayDelegate* tray_delegate =
       static_cast<test::TestSystemTrayDelegate*>(
-          Shell::GetInstance()->system_tray_delegate());
+          WmShell::Get()->system_tray_delegate());
   tray_delegate->set_should_show_display_notification(true);
 
   UpdateDisplay("400x400,200x200");
@@ -585,7 +586,7 @@ TEST_F(TrayDisplayTest, UpdateAfterSuppressDisplayNotification) {
 
   test::TestSystemTrayDelegate* tray_delegate =
       static_cast<test::TestSystemTrayDelegate*>(
-          Shell::GetInstance()->system_tray_delegate());
+          WmShell::Get()->system_tray_delegate());
   tray_delegate->set_should_show_display_notification(true);
 
   // rotate the second.