[Sync] Replace typedef with using.

components/sync/engine_impl/attachments/attachment_downloader_impl.h

 // 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.
 
 #ifndef COMPONENTS_SYNC_ENGINE_IMPL_ATTACHMENTS_ATTACHMENT_DOWNLOADER_IMPL_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_ATTACHMENTS_ATTACHMENT_DOWNLOADER_IMPL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 64 matching lines @@
 
  private:
   FRIEND_TEST_ALL_PREFIXES(AttachmentDownloaderImplTest,
                            ExtractCrc32c_NoHeaders);
   FRIEND_TEST_ALL_PREFIXES(AttachmentDownloaderImplTest, ExtractCrc32c_First);
   FRIEND_TEST_ALL_PREFIXES(AttachmentDownloaderImplTest, ExtractCrc32c_TooLong);
   FRIEND_TEST_ALL_PREFIXES(AttachmentDownloaderImplTest, ExtractCrc32c_None);
   FRIEND_TEST_ALL_PREFIXES(AttachmentDownloaderImplTest, ExtractCrc32c_Empty);
 
   struct DownloadState;
-  typedef std::string AttachmentUrl;
-  typedef std::unordered_map<AttachmentUrl, std::unique_ptr<DownloadState>>
-      StateMap;
-  typedef std::vector<DownloadState*> StateList;
+  using AttachmentUrl = std::string;
+  using StateMap =
+      std::unordered_map<AttachmentUrl, std::unique_ptr<DownloadState>>;
+  using StateList = std::vector<DownloadState*>;
 
   std::unique_ptr<net::URLFetcher> CreateFetcher(
       const AttachmentUrl& url,
       const std::string& access_token);
   void RequestAccessToken(DownloadState* download_state);
   void ReportResult(
       const DownloadState& download_state,
       const DownloadResult& result,
       const scoped_refptr<base::RefCountedString>& attachment_data);
 
@@ skipping 22 matching lines @@
   StateList requests_waiting_for_access_token_;
 
   ModelType model_type_;
 
   DISALLOW_COPY_AND_ASSIGN(AttachmentDownloaderImpl);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_ATTACHMENTS_ATTACHMENT_DOWNLOADER_IMPL_H_