Chrome OS: Fix crash with auto connect notifier.

Also add checks to StubNotificationDisplayService test util class to
catch this in the future (checks match NotificationDisplayServiceImpl
production code).

Bug: 843692
Change-Id: Iebb64687dadf6eb50bffea80e946e8dd3336bac9
Reviewed-on: https://chromium-review.googlesource.com/1062653Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559307}

chrome/browser/notifications/stub_notification_display_service.cc

@@ -181,10 +181,12 @@ void StubNotificationDisplayService::Display(
                      true /* silent */);
 
   NotificationHandler* handler = GetNotificationHandler(notification_type);
-  if (notification_type == NotificationHandler::Type::TRANSIENT)
-    DCHECK(!handler);
-  else
+  if (notification_type == NotificationHandler::Type::TRANSIENT) {
+    CHECK(!handler);
+    CHECK(notification.delegate());
+  } else {
     handler->OnShow(profile_, notification.id());
+  }
 
   notifications_.emplace_back(notification_type, notification,
                               std::move(metadata));

chrome/browser/ui/ash/auto_connect_notifier.cc

@@ -132,7 +132,8 @@ void AutoConnectNotifier::DisplayNotification() {
       message_center::NotifierId(
           message_center::NotifierId::NotifierType::SYSTEM_COMPONENT,
           kNotifierAutoConnect),
-      {} /* optional_fields */, nullptr /* delegate */,
+      {} /* optional_fields */,
+      base::MakeRefCounted<message_center::NotificationDelegate>(),
       gfx::VectorIcon() /* small_image */,
       message_center::SystemNotificationWarningLevel::NORMAL);