Revert of 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 84b240c335d27d85ec3bd8857ea224ab6d6c6041..4d22fd3d12d3d9c489a34af51a732309d8b94636 100644
--- a/ash/common/test/test_system_tray_delegate.cc
+++ b/ash/common/test/test_system_tray_delegate.cc
@@ -16,6 +16,7 @@
 
 namespace {
 
+bool g_system_update_required = false;
 LoginStatus g_initial_status = LoginStatus::USER;
 
 }  // namespace
@@ -70,6 +71,13 @@
   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