message: Minor fixes to ChannelSend.
  Cr-Commit-Position: refs/heads/master@{#29968}
diff: @@ -433,7 +433,7 @@ int32_t ChannelSend::SendRtpAudio(AudioFrameType frameType,
  // undefined for voice for now.
  -1, payloadType,
  /*force_sender_report=*/false)) {
  - return false;
  + return -1;
  }
  // RTCPSender has it's own copy of the timestamp offset, added in
  @@ -491,9 +491,8 @@ ChannelSend::ChannelSend(Clock* clock,
  configuration.overhead_observer = overhead_observer;
  configuration.bandwidth_callback = rtcp_observer_.get();
  configuration.transport_feedback_callback = feedback_observer_proxy_.get();
  - configuration.clock = clock;
  + configuration.clock = (clock ? clock : Clock::GetRealTimeClock());
  configuration.audio = true;
  - configuration.clock = Clock::GetRealTimeClock();
  configuration.outgoing_transport = rtp_transport;
  configuration.paced_sender = rtp_packet_pacer_proxy_.get();
  