ash: Use system tray mojo interface to show system update tray icon

ash/common/test/test_system_tray_delegate.cc

Index: ash/common/test/test_system_tray_delegate.cc
diff --git a/ash/common/test/test_system_tray_delegate.cc b/ash/common/test/test_system_tray_delegate.cc
index 4d22fd3d12d3d9c489a34af51a732309d8b94636..84b240c335d27d85ec3bd8857ea224ab6d6c6041 100644
--- a/ash/common/test/test_system_tray_delegate.cc
+++ b/ash/common/test/test_system_tray_delegate.cc
@@ -16,7 +16,6 @@ namespace test {
 
 namespace {
 
-bool g_system_update_required = false;
 LoginStatus g_initial_status = LoginStatus::USER;
 
 }  // namespace
@@ -71,13 +70,6 @@ bool TestSystemTrayDelegate::IsUserSupervised() const {
   return login_status_ == LoginStatus::SUPERVISED;
 }
 
-void TestSystemTrayDelegate::GetSystemUpdateInfo(UpdateInfo* info) const {
-  DCHECK(info);
-  info->severity = UpdateInfo::UPDATE_NONE;
-  info->update_required = g_system_update_required;
-  info->factory_reset_required = false;
-}
-
 bool TestSystemTrayDelegate::GetSessionStartTime(
     base::TimeTicks* session_start_time) {
   // Just returns TimeTicks::Now(), so the remaining time is always the