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

ash/system/tray/tray_item_more.h

Index: ash/system/tray/tray_item_more.h
diff --git a/ash/system/tray/tray_item_more.h b/ash/system/tray/tray_item_more.h
index ca20f452e66b238afe8926da0eb224966393fd5b..6b82bf5782169d020b9625485df2fa8676e33a60 100644
--- a/ash/system/tray/tray_item_more.h
+++ b/ash/system/tray/tray_item_more.h
@@ -24,9 +24,11 @@ namespace internal {
 // the detailed view of the tray-item that owns it.
 class TrayItemMore : public ActionableView {
  public:
-  TrayItemMore(SystemTrayItem* owner, bool show_more);
+  TrayItemMore(SystemTrayItem* tray, bool show_more);
   virtual ~TrayItemMore();
 
+  SystemTrayItem* tray() const { return tray_; }
+
   void SetLabel(const string16& label);
   void SetImage(const gfx::ImageSkia* image_skia);
   void SetAccessibleName(const string16& name);
@@ -45,7 +47,7 @@ class TrayItemMore : public ActionableView {
   virtual void Layout() OVERRIDE;
   virtual void GetAccessibleState(ui::AccessibleViewState* state) OVERRIDE;
 
-  SystemTrayItem* owner_;
+  SystemTrayItem* tray_;
   // True if |more_| should be shown.
   bool show_more_;
   views::ImageView* icon_;