Remove RtcEventLogImpl forward declaration from rtc_event_log.h

webrtc/logging/rtc_event_log/rtc_event_log.h

 /*
  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 37 matching lines @@
     std::string payload_name;
     int payload_type;
     int rtx_payload_type;
   };
   std::vector<Codec> codecs;
 };
 
 }  // namespace rtclog
 
 class Clock;
-class RtcEventLogImpl;
 struct AudioEncoderRuntimeConfig;
 
 enum class MediaType;
 enum class BandwidthUsage;
 
 enum PacketDirection { kIncomingPacket = 0, kOutgoingPacket };
 enum ProbeFailureReason {
   kInvalidSendReceiveInterval,
   kInvalidSendReceiveRatio,
   kTimeout
@@ skipping 155 matching lines @@
                               int min_probes,
                               int min_bytes) override{};
   void LogProbeResultSuccess(int id, int bitrate_bps) override{};
   void LogProbeResultFailure(int id,
                              ProbeFailureReason failure_reason) override{};
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_LOGGING_RTC_EVENT_LOG_RTC_EVENT_LOG_H_