[Sync] use base::Time in sync

chrome/browser/sync/util/time.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.
+//
+// Time-related sync functions.
+
+#ifndef CHROME_BROWSER_SYNC_UTIL_TIME_H_
+#define CHROME_BROWSER_SYNC_UTIL_TIME_H_
+#pragma once
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/time.h"
+
+namespace browser_sync {
+
+// Converts a time object to the format used in sync protobufs (ms
+// since the Unix epoch).
+int64 TimeToProtoTime(const base::Time& t);
+
+// Converts a time field from sync protobufs to a time object.
+base::Time ProtoTimeToTime(int64 proto_t);
+
+std::string GetTimeDebugString(const base::Time& t);
+
+}  // namespace browser_sync
+
+#endif  // CHROME_BROWSER_SYNC_UTIL_TIME_H_