[Sync] Replace typedef with using.

components/sync/syncable/directory.h

 // Copyright 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.
 
 #ifndef COMPONENTS_SYNC_SYNCABLE_DIRECTORY_H_
 #define COMPONENTS_SYNC_SYNCABLE_DIRECTORY_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 49 matching lines @@
   FULL_DB_VERIFICATION = 2  // Check every entry.  This can be expensive.
 };
 
 // Directory stores and manages EntryKernels.
 //
 // This class is tightly coupled to several other classes via Directory::Kernel.
 // Although Directory's kernel_ is exposed via public accessor it should be
 // treated as pseudo-private.
 class Directory {
  public:
-  typedef std::vector<int64_t> Metahandles;
+  using Metahandles = std::vector<int64_t>;
 
-  typedef std::unordered_map<int64_t, std::unique_ptr<EntryKernel>>
-      MetahandlesMap;
-  typedef std::unordered_map<std::string, EntryKernel*> IdsMap;
-  typedef std::unordered_map<std::string, EntryKernel*> TagsMap;
-  typedef std::string AttachmentIdUniqueId;
-  typedef std::unordered_map<AttachmentIdUniqueId, MetahandleSet>
-      IndexByAttachmentId;
+  using MetahandlesMap =
+      std::unordered_map<int64_t, std::unique_ptr<EntryKernel>>;
+  using IdsMap = std::unordered_map<std::string, EntryKernel*>;
+  using TagsMap = std::unordered_map<std::string, EntryKernel*>;
+  using AttachmentIdUniqueId = std::string;
+  using IndexByAttachmentId =
+      std::unordered_map<AttachmentIdUniqueId, MetahandleSet>;
 
   static const base::FilePath::CharType kSyncDatabaseFilename[];
 
   // The dirty/clean state of kernel fields backed by the share_info table.
   // This is public so it can be used in SaveChangesSnapshot for persistence.
   enum KernelShareInfoStatus {
     KERNEL_SHARE_INFO_INVALID,
     KERNEL_SHARE_INFO_VALID,
     KERNEL_SHARE_INFO_DIRTY
   };
@@ skipping 578 matching lines @@
 
   base::WeakPtrFactory<Directory> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Directory);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_SYNCABLE_DIRECTORY_H_