@leogc didn't know about that..
there's certainly an error there. Here's the output for the link I've used in the post:
render_id: 13
player_id: 1
pipeline_state: kStopped
event: WEBMEDIAPLAYER_CREATED
url: https://video.twimg.com/tweet_video/C49C1WQWYAAIsqM.mp4
total_bytes: 405704
streaming: false
single_origin: true
passed_cors_access_check: false
range_header_supported: true
is_downloading_data: false
platform_pipeline_status_list: 2
error: FFmpegDemuxer: open context failed
pipeline_error: demuxer: could not open