[Sync] Replace typedef with using.

components/sync/model/attachments/attachment_id.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_MODEL_ATTACHMENTS_ATTACHMENT_ID_H_
 #define COMPONENTS_SYNC_MODEL_ATTACHMENTS_ATTACHMENT_ID_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 42 matching lines @@
   // Returns the size (in bytes) the attachment.
   size_t GetSize() const;
 
   // Returns the crc32c the attachment.
   uint32_t GetCrc32c() const;
 
  private:
   // Necessary since we forward-declare sync_pb::AttachmentIdProto; see comments
   // in immutable.h.
   struct ImmutableAttachmentIdProtoTraits {
-    typedef sync_pb::AttachmentIdProto* Wrapper;
+    using Wrapper = sync_pb::AttachmentIdProto*;
     static void InitializeWrapper(Wrapper* wrapper);
     static void DestroyWrapper(Wrapper* wrapper);
     static const sync_pb::AttachmentIdProto& Unwrap(const Wrapper& wrapper);
     static sync_pb::AttachmentIdProto* UnwrapMutable(Wrapper* wrapper);
     static void Swap(sync_pb::AttachmentIdProto* t1,
                      sync_pb::AttachmentIdProto* t2);
   };
 
-  typedef Immutable<sync_pb::AttachmentIdProto,
-                    ImmutableAttachmentIdProtoTraits>
-      ImmutableAttachmentIdProto;
+  using ImmutableAttachmentIdProto =
+      Immutable<sync_pb::AttachmentIdProto, ImmutableAttachmentIdProtoTraits>;
 
   ImmutableAttachmentIdProto proto_;
 
   explicit AttachmentId(sync_pb::AttachmentIdProto* proto);
 };
 
 // All public interfaces use AttachmentIdList. AttachmentIdSet is used in
 // implementations of algorithms where set properties are needed.
-typedef std::vector<AttachmentId> AttachmentIdList;
-typedef std::set<AttachmentId> AttachmentIdSet;
+using AttachmentIdList = std::vector<AttachmentId>;
+using AttachmentIdSet = std::set<AttachmentId>;
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_MODEL_ATTACHMENTS_ATTACHMENT_ID_H_