Ok, this actually seems to be related with THUMB2 support.
Built firefox-5.0+build1+nobinonly without THUMB2 and disabling the ELF hack and now I'm fully able to play webm videos at youtube.
Seems THUMB2 support was enabled while fixing bug 696895, and probably nobody ever tested with webm, as it seems the problem only happens at the libvpx library (firefox keeps it's own version and link it against libxul.so). So a valid workaround for now would be basically disable THUMB2 while we work to enable thumb support again.
Will build again with latest nightly and also report the bug upstream.
Ok, this actually seems to be related with THUMB2 support.
Built firefox- 5.0+build1+ nobinonly without THUMB2 and disabling the ELF hack and now I'm fully able to play webm videos at youtube.
Seems THUMB2 support was enabled while fixing bug 696895, and probably nobody ever tested with webm, as it seems the problem only happens at the libvpx library (firefox keeps it's own version and link it against libxul.so). So a valid workaround for now would be basically disable THUMB2 while we work to enable thumb support again.
Will build again with latest nightly and also report the bug upstream.