Add missing #include around sequenced_worker_pool.h in //chrome

chrome/browser/extensions/extension_gcm_app_handler_unittest.cc

 // Copyright 2014 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/extensions/extension_gcm_app_handler.h"
 
 #include <memory>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/api/gcm/gcm_api.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/test_extension_service.h"
 #include "chrome/browser/extensions/test_extension_system.h"
 #include "chrome/browser/gcm/gcm_product_util.h"
 #include "chrome/browser/gcm/gcm_profile_service_factory.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 449 matching lines @@
 
   // App handler is removed when the extension is updated to the version that
   // has GCM permission removed.
   UpdateExtension(extension.get(), "good2.crx");
   waiter()->PumpUILoop();
   EXPECT_TRUE(gcm_app_handler()->app_handler_count_drop_to_zero());
   EXPECT_FALSE(HasAppHandlers(extension->id()));
 }
 
 }  // namespace extensions