Initialize the message center as part of the testing browser process

chrome/browser/notifications/notification_display_service_factory.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/notifications/notification_display_service_factory.h"
 
 #include "base/command_line.h"
 #include "base/memory/singleton.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/notifications/message_center_display_service.h"
@@ skipping 27 matching lines @@
 
 // Selection of the implementation works as follows:
 //   - Android always uses the NativeNotificationDisplayService.
 //   - Mac uses the MessageCenterDisplayService by default, but can use the
 //     NativeNotificationDisplayService by using the chrome://flags or via
 //     the --enable-features=NativeNotifications command line flag.
 //   - All other platforms always use the MessageCenterDisplayService.
 KeyedService* NotificationDisplayServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
 #if defined(OS_ANDROID)
+  if (!g_browser_process->notification_platform_bridge()) {
+    DCHECK(Profile::FromBrowserContext(context)->AsTestingProfile());
+    return nullptr;
+  }
   return new NativeNotificationDisplayService(
       Profile::FromBrowserContext(context),
       g_browser_process->notification_platform_bridge());
 #elif defined(OS_MACOSX)
   if (base::FeatureList::IsEnabled(features::kNativeNotifications)) {
     return new NativeNotificationDisplayService(
         Profile::FromBrowserContext(context),
         g_browser_process->notification_platform_bridge());
   }
 #endif
+  if (!g_browser_process->notification_ui_manager()) {
+    DCHECK(Profile::FromBrowserContext(context)->AsTestingProfile());
+    return nullptr;
+  }
   return new MessageCenterDisplayService(
       Profile::FromBrowserContext(context),
       g_browser_process->notification_ui_manager());
 }
 
 content::BrowserContext*
 NotificationDisplayServiceFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextOwnInstanceInIncognito(context);
 }