Make RtpSenderAudio not inherit from DtmfQueue

webrtc/modules/rtp_rtcp/source/dtmf_queue.cc

 /*
  *  Copyright (c) 2011 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 41 matching lines @@
           next_empty_index_ * sizeof(uint8_t));
 
   next_empty_index_--;
   return 0;
 }
 
 bool DTMFqueue::PendingDTMF() {
   rtc::CritScope lock(&dtmf_critsect_);
   return next_empty_index_ > 0;
 }
-
-void DTMFqueue::ResetDTMF() {
-  rtc::CritScope lock(&dtmf_critsect_);
-  next_empty_index_ = 0;
-}
 }  // namespace webrtc