www-client/chromium applies "chromium-disable-vp8-r1.patch" to remove VP8 support. A comment in the ebuild gives the following reason:
"Disable VP8 until we have a recent enough system-provided ffmpeg."
However, media-video/ffmpeg-0.6 has been in the tree for quite a while and does support VP8 if USE="vpx" is set. Therefore, it should be possible to enable VP8 with a use-flag that adds the appropriate dependency.
I'll upload a patch against the chromium-6.0.472.0.ebuild that works for me.
Created attachment 239955 [details, diff]
Add USE="vpx" to enable VP8 support
Thank you for the patch. I'm going to unconditionally require ffmpeg[vpx] and drop the patch after we have a dev channel release with a newer branch than 472.
More recent ebuilds use bundled ffmpeg. I will likely use something like this patch when switching back.