Make the default value of rtcp-mux policy to required.

webrtc/api/peerconnectioninterface.h

 /*
  *  Copyright 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 262 matching lines @@
     static const int kUndefined = -1;
     // Default maximum number of packets in the audio jitter buffer.
     static const int kAudioJitterBufferMaxPackets = 50;
     // TODO(pthatcher): Rename this ice_transport_type, but update
     // Chromium at the same time.
     IceTransportsType type = kAll;
     // TODO(pthatcher): Rename this ice_servers, but update Chromium
     // at the same time.
     IceServers servers;
     BundlePolicy bundle_policy = kBundlePolicyBalanced;
-    RtcpMuxPolicy rtcp_mux_policy = kRtcpMuxPolicyNegotiate;
+    RtcpMuxPolicy rtcp_mux_policy = kRtcpMuxPolicyRequire;
     TcpCandidatePolicy tcp_candidate_policy = kTcpCandidatePolicyEnabled;
     CandidateNetworkPolicy candidate_network_policy =
         kCandidateNetworkPolicyAll;
     int audio_jitter_buffer_max_packets = kAudioJitterBufferMaxPackets;
     bool audio_jitter_buffer_fast_accelerate = false;
     int ice_connection_receiving_timeout = kUndefined;         // ms
     int ice_backup_candidate_pair_ping_interval = kUndefined;  // ms
     ContinualGatheringPolicy continual_gathering_policy = GATHER_ONCE;
     std::vector<rtc::scoped_refptr<rtc::RTCCertificate>> certificates;
     bool prioritize_most_likely_ice_candidate_pairs = false;
@@ skipping 428 matching lines @@
     cricket::WebRtcVideoEncoderFactory* encoder_factory,
     cricket::WebRtcVideoDecoderFactory* decoder_factory) {
   return CreatePeerConnectionFactory(
       worker_and_network_thread, worker_and_network_thread, signaling_thread,
       default_adm, encoder_factory, decoder_factory);
 }
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_PEERCONNECTIONINTERFACE_H_