Add update available icon in system tray

ash/system/tray/system_tray_controller.h

Index: ash/system/tray/system_tray_controller.h
diff --git a/ash/system/tray/system_tray_controller.h b/ash/system/tray/system_tray_controller.h
index 74e5268a057711aa054d3e016919c15d76cc604f..8217def1e38efe2982d8fd7da3d08ed98a4b9465 100644
--- a/ash/system/tray/system_tray_controller.h
+++ b/ash/system/tray/system_tray_controller.h
@@ -46,6 +46,7 @@ class ASH_EXPORT SystemTrayController
   void ShowPowerSettings();
   void ShowChromeSlow();
   void ShowIMESettings();
+  void ShowAboutChromeOS();
   void ShowHelp();
   void ShowAccessibilityHelp();
   void ShowAccessibilitySettings();
@@ -74,6 +75,7 @@ class ASH_EXPORT SystemTrayController
   void ShowUpdateIcon(mojom::UpdateSeverity severity,
                       bool factory_reset_required,
                       mojom::UpdateType update_type) override;
+  void ShowUpdateOverCellularAvailableIcon() override;
 
  private:
   // Client interface in chrome browser. May be null in tests.