WebM VP8/Vorbis marked as video/webm; codecs="vp8, vorbis":
WebM VP8/Vorbis marked as video/webm:
WebM VP8/Vorbis unmarked:
WebM VP8 (no audio) marked as video/webm; codecs="vp8":
WebM VP8 (no audio) marked as video/webm:
WebM VP8 (no audio) unmarked: