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}
   bool ReceiverWasAdded(const RtpTransceiverState& transceiver_state) {
    DCHECK(handler_);
     uintptr_t receiver_id = RTCRtpReceiver::getId(
         transceiver_state.receiver_state()->webrtc_receiver().get());
     for (const auto& receiver : handler_->rtp_receivers_) {
      if (receiver->Id() == receiver_id)
        return false;
    }
    return true;
  }

   bool ReceiverWasAdded(const RtpTransceiverState& transceiver_state) {
     uintptr_t receiver_id = RTCRtpReceiver::getId(
         transceiver_state.receiver_state()->webrtc_receiver().get());
     for (const auto& receiver : handler_->rtp_receivers_) {
      if (receiver->Id() == receiver_id)
        return false;
    }
    return true;
  }
