Implement a poor man's PostAfterStartupTask() function.

content/content_browser.gypi

 # 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.
 
 {
   'dependencies': [
     '../base/base.gyp:base_static',
     '../crypto/crypto.gyp:crypto',
     '../device/vibration/vibration.gyp:device_vibration',
     '../device/vibration/vibration.gyp:device_vibration_mojo_bindings',
@@ skipping 32 matching lines @@
     '../skia/skia.gyp:skia',
     'content_common_mojo_bindings.gyp:content_common_mojo_bindings',
   ],
   'include_dirs': [
     '..',
     '<(INTERMEDIATE_DIR)',
   ],
   'variables': {
     'public_browser_sources': [
       'public/browser/access_token_store.h',
+      'public/browser/after_startup_task_poster.h',
       'public/browser/android/compositor.h',
       'public/browser/android/compositor_client.h',
       'public/browser/android/content_protocol_handler.h',
       'public/browser/android/content_view_core.h',
       'public/browser/android/content_view_layer_renderer.h',
       'public/browser/android/devtools_auth.h',
       'public/browser/android/download_controller_android.h',
       'public/browser/android/external_video_surface_container.h',
       'public/browser/android/synchronous_compositor.h',
       'public/browser/android/synchronous_compositor_client.h',
@@ skipping 233 matching lines @@
       'browser/accessibility/browser_accessibility_manager_android.h',
       'browser/accessibility/browser_accessibility_manager_mac.h',
       'browser/accessibility/browser_accessibility_manager_mac.mm',
       'browser/accessibility/browser_accessibility_manager_win.cc',
       'browser/accessibility/browser_accessibility_manager_win.h',
       'browser/accessibility/browser_accessibility_state_impl.cc',
       'browser/accessibility/browser_accessibility_state_impl.h',
       'browser/accessibility/browser_accessibility_state_impl_win.cc',
       'browser/accessibility/browser_accessibility_win.cc',
       'browser/accessibility/browser_accessibility_win.h',
+      'browser/after_startup_task_poster_impl.cc',
+      'browser/after_startup_task_poster_impl.h',
       'browser/android/animation_utils.h',
       'browser/android/browser_jni_registrar.cc',
       'browser/android/browser_jni_registrar.h',
       'browser/android/browser_startup_controller.cc',
       'browser/android/browser_startup_controller.h',
       'browser/android/browser_surface_texture_manager.cc',
       'browser/android/browser_surface_texture_manager.h',
       'browser/android/child_process_launcher_android.cc',
       'browser/android/child_process_launcher_android.h',
       'browser/android/composited_touch_handle_drawable.cc',
@@ skipping 1656 matching lines @@
         'browser/media/media_web_contents_observer.h',
       ],
     }],
     ['OS == "linux" and use_openssl==1', {
       'dependencies': [
         '../third_party/boringssl/boringssl.gyp:boringssl',
       ],
     }],
   ],
 }