Fix the timestamp generation for webrtc native log.

chrome/common/media/webrtc_logging_message_data.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 CHROME_COMMON_MEDIA_WEBRTC_LOGGING_MESSAGE_DATA_H_
+#define CHROME_COMMON_MEDIA_WEBRTC_LOGGING_MESSAGE_DATA_H_
+
+#include <string>
+
+#include "base/time/time.h"
+
+// A struct representing a logging message with its creation time.
+struct WebRtcLoggingMessageData {
+  WebRtcLoggingMessageData();
+  WebRtcLoggingMessageData(base::Time time, const std::string& message);
+
+  // Returns a string formatted as "[XXX:YYY] $message", where "[XXX:YYY]" is
+  // the timestamp relative to |start_time| converted to seconds (XXX) plus
+  // milliseconds (YYY).
+  std::string Format(base::Time start_time) const;
+
+  base::Time timestamp;
+  std::string message;
+};
+
+#endif  // CHROME_COMMON_MEDIA_WEBRTC_LOGGING_MESSAGE_DATA_H_