Check weak pointers in RTCPeerConnectionHandler::WebRtcSetDescriptionObserverImpl

Bug: 912074
Change-Id: I8ba86751f5d5bf12db51520f985ef0d3dae63ed8
Reviewed-on: https://chromium-review.googlesource.com/c/1411916
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622945}
void RTCPeerConnectionHandler::OnRenegotiationNeeded() {
  DCHECK(task_runner_->RunsTasksInCurrentSequence());
  TRACE_EVENT0("webrtc", "RTCPeerConnectionHandler::OnRenegotiationNeeded");
  if (peer_connection_tracker_)
    peer_connection_tracker_->TrackOnRenegotiationNeeded(this);
  if (!is_closed_)
    client_->NegotiationNeeded();
}

void RTCPeerConnectionHandler::OnRenegotiationNeeded() {
  DCHECK(task_runner_->RunsTasksInCurrentSequence());
  TRACE_EVENT0("webrtc", "RTCPeerConnectionHandler::OnRenegotiationNeeded");
  if (peer_connection_tracker_)
    peer_connection_tracker_->TrackOnRenegotiationNeeded(this);
  if (!is_closed_)
    client_->NegotiationNeeded();
}
