Crash report: https://crash-stats.mozilla.org/report/index/f8e02a1c-1156-4756-99f4-288cf0211214

Reason: STATUS_STACK_BUFFER_OVERRUN / FAST_FAIL_FATAL_APP_EXIT

Top 10 frames of crashing thread:

0 ucrtbase.dll abort 
1 xul.dll rtc::FatalMessage::~FatalMessage third_party/libwebrtc/webrtc/rtc_base/checks.cc:69
2 xul.dll webrtc::RtpPacketizerH264::PacketizeSingleNalu third_party/libwebrtc/webrtc/modules/rtp_rtcp/source/rtp_format_h264.cc:296
3 xul.dll webrtc::RtpPacketizerH264::GeneratePackets third_party/libwebrtc/webrtc/modules/rtp_rtcp/source/rtp_format_h264.cc:178
4 xul.dll webrtc::RtpPacketizerH264::SetPayloadData third_party/libwebrtc/webrtc/modules/rtp_rtcp/source/rtp_format_h264.cc:170
5 xul.dll webrtc::RTPSenderVideo::SendVideo third_party/libwebrtc/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc:386
6 xul.dll webrtc::RTPSender::SendOutgoingData third_party/libwebrtc/webrtc/modules/rtp_rtcp/source/rtp_sender.cc:454
7 xul.dll webrtc::ModuleRtpRtcpImpl::SendOutgoingData third_party/libwebrtc/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc:462
8 xul.dll webrtc::PayloadRouter::OnEncodedImage third_party/libwebrtc/webrtc/video/payload_router.cc:219
9 xul.dll webrtc::internal::VideoSendStreamImpl::OnEncodedImage third_party/libwebrtc/webrtc/video/video_send_stream.cc:1012

This is libwebrtc calling abort() which on Windows can only be caught via Windows Error Reporting. Unsure if there are similar crashes on other platforms under different signatures; it's possible.

Looks like bug 1731583.