Fix issues with RestartingSendStreamPreservesRtpStatesWithRtx

webrtc/modules/rtp_rtcp/source/rtp_sender_audio.cc

 /*
  *  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 400 matching lines @@
   uint8_t dtmfbuffer[IP_PACKET_SIZE];
   uint8_t sendCount = 1;
   int32_t retVal = 0;
 
   if (ended) {
     // resend last packet in an event 3 times
     sendCount = 3;
   }
   do {
     // Send DTMF data
-    rtp_sender_->BuildRtpHeader(dtmfbuffer, dtmf_payload_type, marker_bit,
-                                dtmf_timestamp, clock_->TimeInMilliseconds());
+    int32_t header_length = rtp_sender_->BuildRtpHeader(
+        dtmfbuffer, dtmf_payload_type, marker_bit, dtmf_timestamp,
+        clock_->TimeInMilliseconds());
+    if (header_length <= 0)
+      return -1;
 
     // reset CSRC and X bit
     dtmfbuffer[0] &= 0xe0;
 
     // Create DTMF data
     /*    From RFC 2833:
 
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
@@ skipping 17 matching lines @@
         "timestamp", dtmf_timestamp, "seqnum", rtp_sender_->SequenceNumber());
     retVal = rtp_sender_->SendToNetwork(dtmfbuffer, 4, 12, rtc::TimeMillis(),
                                         kAllowRetransmission,
                                         RtpPacketSender::kHighPriority);
     sendCount--;
   } while (sendCount > 0 && retVal == 0);
 
   return retVal;
 }
 }  // namespace webrtc