As of http://trac.webkit.org/log/?verbose=on&rev=135515&stop_rev=135510, media/video-seek-past-end-playing.html is crashing intermittently on SnowLeopard / Win7.
r135500 seems like the only video related change around then but this might be wrong or a distraction.
crash log for DumpRenderTree (pid 12948):
STDERR: [12948:10232:1692532:FATAL:video_renderer_base.cc(580)] Check failed: !pending_read_.
R135500 should not be involved when playing video. The mediastream codepaths and the media playing codepaths don't touch much.
also effects media/video-duration-known-after-eos.html on win7, SnowLeopard, Lion.
*** This bug has been marked as a duplicate of bug 103093 ***
media/video-currentTime-set.html crashing the same way.