No sound with latest firefox under current

[Dave Tyson <dtyson%anduin.org.uk@localhost>]

Just been rebuilding packages on an amd64 system running current. Sound 
working OK in KDE, mplayer etc. No pulseaudio installed deliberately!

Installed firefox 50.1.0 and tried youtube, but no sound. Fiddled around but 
couldn't find any knobs to twiddle.

Pulled in the firefox source for 49.2 from a few weeks ago and 
compiled/installed that - sound works perfectly.

mk.conf:
LIBDVDCSS_MASTER_SITES=http://download.videolan.org/pub/libdvdcss/
ALLOW_VULNERABLE_PACKAGES=1
PKG_DEFAULT_OPTIONS+= cups
PKG_DEFAULT_OPTIONS+= -pulseaudio +oss
ACCEPTABLE_LICENSES+= lame-license
ACCEPTABLE_LICENSES+= mozilla-trademark-license
ACCEPTABLE_LICENSES+= libdvdcss-license
ACCEPTABLE_LICENSES+= unrar-license
ACCEPTABLE_LICENSES+= mplayer-codec-license
ACCEPTABLE_LICENSES+= pine-license
ACCEPTABLE_LICENSES+= lame-license
ACCEPTABLE_LICENSES+= ms-ttf-license
PKG_OPTIONS.pinentry= qt
PKG_OPTIONS.firefox+= official-mozilla-branding
PKG_OPTIONS.firefox+= oss

Anyone else seeing this problem? 

Dave

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