It looks like the httpd.js can fail to write data when running media mochitests. This causes our media decoders that are waiting for data in MediaCacheStream::Read() to never get it, and this causes test time outs. The error I'm seeing on the console is: System JS : ERROR /home/cpearce/src/mozilla/orange/objdir/_tests/testing/mochitest/httpd.js:2854 NS_ERROR_UNEXPECTED: Component returned failure code: 0x8000ffff (NS_ERROR_UNEXPECTED) [nsIBinaryOutputStream.writeByteArray] STR: 1. Apply patches from bug 846769 (to prevent assertion failures) 2. ./mach mochitest-plain content/media/test/test_seek.html --run-until-failure --repeat 100000 3. Wait... In one run it took only 5 minutes for this failure to occur, though I've looped on this test much longer and *not* got this error. I've also seen what looks like this happen once on Windows as well, with STR as above (but with gSeekTests only containing Ogg files). Changing gSeekTests to only contain files used by the GStreamer backend (MP4 and MP3) may increase the repro rate on Linux, but this bug repros without doing that on Windows (but at a very low rate).

Mass closing do to inactivity. Feel free to re-open if still needed.