Use MetadataChangeList and EntityChangeList in SharedModelTypeProcessor

sync/api/entity_change.h

 // Copyright 2015 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 SYNC_API_ENTITY_CHANGE_H_
 #define SYNC_API_ENTITY_CHANGE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 16 matching lines @@
 
   virtual ~EntityChange();
 
   std::string client_key() const { return client_key_; }
   ChangeType type() const { return type_; }
   const EntityData& data() const { return data_.value(); }
 
  private:
   EntityChange(std::string client_key, ChangeType type, EntityDataPtr data);
 
-  const std::string client_key_;
-  const ChangeType type_;
-  const EntityDataPtr data_;
+  std::string client_key_;
+  ChangeType type_;
+  EntityDataPtr data_;
 };
 
 typedef std::vector<EntityChange> EntityChangeList;
 
 }  // namespace syncer_v2
 
 #endif  // SYNC_API_ENTITY_CHANGE_H_