Remove update icon after user confirms download

ash/system/tray/system_tray_notifier.cc

Index: ash/system/tray/system_tray_notifier.cc
diff --git a/ash/system/tray/system_tray_notifier.cc b/ash/system/tray/system_tray_notifier.cc
index 661c9f63cb921d236e155c5b0837ca9b5d55cd96..4f76c26105d07f52ddd93d0963be3691704d86e0 100644
--- a/ash/system/tray/system_tray_notifier.cc
+++ b/ash/system/tray/system_tray_notifier.cc
@@ -17,6 +17,7 @@
 #include "ash/system/session/logout_button_observer.h"
 #include "ash/system/status_area_focus_observer.h"
 #include "ash/system/tray_tracing.h"
+#include "ash/system/update/update_observer.h"
 #include "ash/system/virtual_keyboard/virtual_keyboard_observer.h"
 
 namespace ash {
@@ -256,6 +257,19 @@ void SystemTrayNotifier::NotifyTracingModeChanged(bool value) {
     observer.OnTracingModeChanged(value);
 }
 
+void SystemTrayNotifier::AddUpdateObserver(UpdateObserver* observer) {
+  update_observers_.AddObserver(observer);
+}
+
+void SystemTrayNotifier::RemoveUpdateObserver(UpdateObserver* observer) {
+  update_observers_.RemoveObserver(observer);
+}
+
+void SystemTrayNotifier::NotifyUpdateOverCellularTargetSet(bool success) {
+  for (auto& observer : update_observers_)
+    observer.OnUpdateOverCellularTargetSet(success);
+}
+
 void SystemTrayNotifier::AddVirtualKeyboardObserver(
     VirtualKeyboardObserver* observer) {
   virtual_keyboard_observers_.AddObserver(observer);