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

chrome/browser/component_updater/pepper_flash_component_installer.cc

 // Copyright (c) 2013 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/component_updater/pepper_flash_component_installer.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/base_paths.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/json/json_reader.h"
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/version.h"
 #include "build/build_config.h"
 #include "chrome/browser/component_updater/component_installer_errors.h"
 #include "chrome/browser/plugins/plugin_prefs.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_content_client.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pepper_flash.h"
 #include "chrome/common/ppapi_utils.h"
@@ skipping 332 matching lines @@
   std::unique_ptr<ComponentInstallerTraits> traits(
       new FlashComponentInstallerTraits);
   // |cus| will take ownership of |installer| during installer->Register(cus).
   DefaultComponentInstaller* installer =
       new DefaultComponentInstaller(std::move(traits));
   installer->Register(cus, base::Closure());
 #endif  // defined(GOOGLE_CHROME_BUILD)
 }
 
 }  // namespace component_updater