Update NetLog to be thread safe.

chrome/browser/net/net_log_logger.h

 // Copyright (c) 2010 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_NET_NET_LOG_LOGGER_H_
 #define CHROME_BROWSER_NET_NET_LOG_LOGGER_H_
 #pragma once
 
 #include "chrome/browser/net/chrome_net_log.h"
 
 // NetLogLogger watches the NetLog event stream, and sends all entries to
 // VLOG(1).  This is to debug errors that prevent getting to the
 // about:net-internals page.
-class NetLogLogger : public ChromeNetLog::Observer {
+class NetLogLogger : public ChromeNetLog::ThreadSafeObserver {
  public:
   NetLogLogger();
   ~NetLogLogger();
 
-  // Observer implementation:
+  // ThreadSafeObserver implementation:
   virtual void OnAddEntry(net::NetLog::EventType type,
                           const base::TimeTicks& time,
                           const net::NetLog::Source& source,
                           net::NetLog::EventPhase phase,
                           net::NetLog::EventParameters* params);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NetLogLogger);
 };
 
 #endif  // CHROME_BROWSER_NET_NET_LOG_LOGGER_H_