Add update available icon in system tray

ash/system/update/tray_update.h

Index: ash/system/update/tray_update.h
diff --git a/ash/system/update/tray_update.h b/ash/system/update/tray_update.h
index 6d3a9c001ed08bafebe8d7d6e15af165e262e8c6..5a5c84a62ddbd30797a5c86d9bebbb0b442c6a24 100644
--- a/ash/system/update/tray_update.h
+++ b/ash/system/update/tray_update.h
@@ -38,6 +38,11 @@ class ASH_EXPORT TrayUpdate : public TrayImageItem {
                       bool factory_reset_required,
                       mojom::UpdateType update_type);
 
+  // Shows an icon in the system tray indicating that a software update is
+  // available but user's agreement is required as current connection is
+  // cellular. Once shown the icon persists until reboot.
+  void ShowUpdateOverCellularAvailableIcon();
+
  private:
   FRIEND_TEST_ALL_PREFIXES(TrayUpdateTest, VisibilityAfterUpdate);
   FRIEND_TEST_ALL_PREFIXES(TrayUpdateTest, VisibilityAfterFlashUpdate);
@@ -56,10 +61,11 @@ class ASH_EXPORT TrayUpdate : public TrayImageItem {
   // If an external monitor is connected then the system tray may be created
   // after the update data is sent from chrome, so share the update info between
   // all instances.
-  static bool update_required_;
+  static bool upgrade_required_;

[weidongg, 2017/05/15 04:54:13]

I refactored here to distinguish 'update' with 'upgrade'. It seems upgrade does
not include the downloading process of a software update, but I am not sure.

   static mojom::UpdateSeverity severity_;
   static bool factory_reset_required_;
   static mojom::UpdateType update_type_;
+  static bool update_over_cellular_available_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayUpdate);
 };