Stop using shell::GetInstance()->system_tray() in system tray items

ash/system/tray/tray_notification_view.cc

Index: ash/system/tray/tray_notification_view.cc
diff --git a/ash/system/tray/tray_notification_view.cc b/ash/system/tray/tray_notification_view.cc
index d787e9209cf37959b76765fbfc53ebc3a284969f..2c4929b507a3d7ae1d4677f4152746611368845d 100644
--- a/ash/system/tray/tray_notification_view.cc
+++ b/ash/system/tray/tray_notification_view.cc
@@ -23,8 +23,8 @@ const int kNotificationButtonWidth = 32;
 namespace ash {
 namespace internal {
 
-TrayNotificationView::TrayNotificationView(SystemTrayItem* tray, int icon_id)
-    : tray_(tray),
+TrayNotificationView::TrayNotificationView(SystemTrayItem* owner, int icon_id)
+    : owner_(owner),
       icon_id_(icon_id),
       icon_(NULL) {
 }
@@ -140,12 +140,12 @@ void TrayNotificationView::OnClickAction() {
 }
 
 void TrayNotificationView::OnSlideOut() {
-  tray_->HideNotificationView();
+  owner_->HideNotificationView();
 }
 
 void TrayNotificationView::HandleClose() {
   OnClose();
-  tray_->HideNotificationView();
+  owner_->HideNotificationView();
 }
 
 void TrayNotificationView::HandleClickAction() {