Implement a poor man's PostAfterStartupTask() function.

content/public/browser/content_browser_client.cc

 // Copyright (c) 2012 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 "content/public/browser/content_browser_client.h"
 
 #include "base/files/file_path.h"
+#include "content/browser/after_startup_task_poster_impl.h"
 #include "ui/gfx/image/image_skia.h"
 #include "url/gurl.h"
 
 namespace content {
 
 BrowserMainParts* ContentBrowserClient::CreateBrowserMainParts(
     const MainFunctionParams& parameters) {
   return nullptr;
 }
 
+AfterStartupTaskPoster* ContentBrowserClient::GetAfterStartupTaskPoster() {
+  static DefaultAfterStartupTaskPoster default_task_poster;
+  return &default_task_poster;
+}
+
 WebContentsViewDelegate* ContentBrowserClient::GetWebContentsViewDelegate(
     WebContents* web_contents) {
   return nullptr;
 }
 
 GURL ContentBrowserClient::GetEffectiveURL(BrowserContext* browser_context,
                                            const GURL& url) {
   return url;
 }
 
@@ skipping 333 matching lines @@
 
 #if defined(VIDEO_HOLE)
 ExternalVideoSurfaceContainer*
 ContentBrowserClient::OverrideCreateExternalVideoSurfaceContainer(
     WebContents* web_contents) {
   return nullptr;
 }
 #endif
 
 }  // namespace content