Support multiple rtx codecs.

webrtc/modules/rtp_rtcp/include/rtp_rtcp.h

 /*
  *  Copyright (c) 2012 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 231 matching lines @@
 
     // Sets the SSRC to use when sending RTX packets. This doesn't enable RTX,
     // only the SSRC is set.
     virtual void SetRtxSsrc(uint32_t ssrc) = 0;
 
     // Sets the payload type to use when sending RTX packets. Note that this
     // doesn't enable RTX, only the payload type is set.
     virtual void SetRtxSendPayloadType(int payload_type,
                                        int associated_payload_type) = 0;
 
-    // Gets the payload type pair of (RTX, associated) to use when sending RTX
-    // packets.
-    virtual std::pair<int, int> RtxSendPayloadType() const = 0;
-
     /*
     *   sends kRtcpByeCode when going from true to false
     *
     *   sending - on/off
     *
     *   return -1 on failure else 0
     */
     virtual int32_t SetSendingStatus(bool sending) = 0;
 
     /*
@@ skipping 383 matching lines @@
 
     /*
     *   send a request for a keyframe
     *
     *   return -1 on failure else 0
     */
     virtual int32_t RequestKeyFrame() = 0;
 };
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_RTP_RTCP_INCLUDE_RTP_RTCP_H_