[Sync] use base::Time in sync

chrome/browser/sync/internal_api/base_node.h

 // Copyright (c) 2011 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 CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_
 #define CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 55 matching lines @@
   // will return FALSE.
   virtual bool InitByClientTagLookup(syncable::ModelType model_type,
       const std::string& tag) = 0;
 
   // Each object is identified by a 64-bit id (internally, the syncable
   // metahandle).  These ids are strictly local handles.  They will persist
   // on this client, but the same object on a different client may have a
   // different ID value.
   virtual int64 GetId() const;
 
-  // Returns the modification time of the object (in TimeTicks internal format).
-  int64 GetModificationTime() const;
+  // Returns the modification time of the object.
+  const base::Time& GetModificationTime() const;
 
   // Nodes are hierarchically arranged into a single-rooted tree.
   // InitByRootLookup on ReadNode allows access to the root. GetParentId is
   // how you find a node's parent.
   int64 GetParentId() const;
 
   // Nodes are either folders or not.  This corresponds to the IS_DIR property
   // of syncable::Entry.
   bool GetIsFolder() const;
 
@@ skipping 127 matching lines @@
 
   friend class SyncApiTest;
   FRIEND_TEST_ALL_PREFIXES(SyncApiTest, GenerateSyncableHash);
 
   DISALLOW_COPY_AND_ASSIGN(BaseNode);
 };
 
 }  // namespace sync_api
 
 #endif  // CHROME_BROWSER_SYNC_INTERNAL_API_BASE_NODE_H_