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

ash/system/tray/tray_image_item.cc

Index: ash/system/tray/tray_image_item.cc
diff --git a/ash/system/tray/tray_image_item.cc b/ash/system/tray/tray_image_item.cc
index 65939c0f118c5da02067c6cf56b81dc4238d2394..f5a3e89ac35b4ab84f1faec97433ec9dff33d128 100644
--- a/ash/system/tray/tray_image_item.cc
+++ b/ash/system/tray/tray_image_item.cc
@@ -14,8 +14,9 @@
 namespace ash {
 namespace internal {
 
-TrayImageItem::TrayImageItem(int resource_id)
-    : resource_id_(resource_id),
+TrayImageItem::TrayImageItem(SystemTray* system_tray, int resource_id)
+    : SystemTrayItem(system_tray),
+      resource_id_(resource_id),
       tray_view_(NULL) {
 }
 
@@ -35,7 +36,7 @@ void TrayImageItem::SetImageFromResourceId(int resource_id) {
 
 views::View* TrayImageItem::CreateTrayView(user::LoginStatus status) {
   CHECK(tray_view_ == NULL);
-  tray_view_ = new TrayItemView;
+  tray_view_ = new TrayItemView(this);
   tray_view_->CreateImageView();
   tray_view_->image_view()->SetImage(ui::ResourceBundle::GetSharedInstance().
       GetImageNamed(resource_id_).ToImageSkia());