Add QUIC_PLOG to gfe/quic/platform and use it in TunDevice.

net/quic/platform/api/quic_logging.h

 // Copyright (c) 2017 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 NET_QUIC_PLATFORM_API_QUIC_LOGGING_H_
 #define NET_QUIC_PLATFORM_API_QUIC_LOGGING_H_
 
 #include "net/quic/platform/impl/quic_logging_impl.h"
 
 // Please note following QUIC_LOG are platform dependent:
 // INFO severity can be degraded (to VLOG(1) or DVLOG(1)).
 // Some platforms may not support QUIC_LOG_FIRST_N or QUIC_LOG_EVERY_N_SEC, and
 // they would simply be translated to LOG.
 
 #define QUIC_DVLOG(verbose_level) QUIC_DVLOG_IMPL(verbose_level)
 #define QUIC_DLOG(severity) QUIC_DLOG_IMPL(severity)
 #define QUIC_DLOG_IF(severity, condition) QUIC_DLOG_IF_IMPL(severity, condition)
 #define QUIC_LOG(severity) QUIC_LOG_IMPL(severity)
 #define QUIC_LOG_FIRST_N(severity, n) QUIC_LOG_FIRST_N_IMPL(severity, n)
 #define QUIC_LOG_EVERY_N_SEC(severity, seconds) \
   QUIC_LOG_EVERY_N_SEC_IMPL(severity, seconds)
 #define QUIC_LOG_IF(severity, condition) QUIC_LOG_IF_IMPL(severity, condition)
 
 #define QUIC_PREDICT_FALSE(x) QUIC_PREDICT_FALSE_IMPL(x)
 
 #define QUIC_NOTREACHED() QUIC_NOTREACHED_IMPL()
 
+#define QUIC_PLOG(severity) QUIC_PLOG_IMPL(severity)
+
 #endif  // NET_QUIC_PLATFORM_API_QUIC_LOGGING_H_