ash: Add a unit test for the system update tray item

ash/system/tray/system_tray.h

Index: ash/system/tray/system_tray.h
diff --git a/ash/system/tray/system_tray.h b/ash/system/tray/system_tray.h
index fb5f4d8f6c58dfac0a882fc6954e9bf381d926f0..43d6674057a0dc4c201f533f931bef19bbd50ce2 100644
--- a/ash/system/tray/system_tray.h
+++ b/ash/system/tray/system_tray.h
@@ -27,6 +27,7 @@ class SystemTrayDelegate;
 class SystemTrayItem;
 class TrayAccessibility;
 class TrayDate;
+class TrayUpdate;
 class TrayUser;
 
 // There are different methods for creating bubble views.
@@ -157,6 +158,8 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   // Gets tray_date_ for browser tests.
   TrayDate* GetTrayDateForTesting() const;
 
+  TrayUpdate* GetTrayUpdateForTesting() const;

[stevenjb, 2016/06/10 22:56:30]

nit: Replace the comments in 155 and 158 with "Unit test getters" (or just
remove them all)

[James Cook, 2016/06/10 23:15:03]

I removed the comments, the method names are enough.

+
  private:
   // Creates the default set of items for the sytem tray.
   void CreateItems(SystemTrayDelegate* delegate);
@@ -242,6 +245,7 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   TrayAccessibility* tray_accessibility_;  // not owned
   TrayCast* tray_cast_;
   TrayDate* tray_date_;
+  TrayUpdate* tray_update_;
 
   // A reference to the Screen share and capture item.
   ScreenTrayItem* screen_capture_tray_item_;  // not owned