It doesn't make sense to do this. The media will already be at the beginning, since we're just started loading it. Additionally, since this seek is executed after the user's script (for the loadedmetadata event), it can clobber the user's attempt to seek, since we could seek to the user's requested location, then immediately seek back to the media start.
Created attachment 352956 [details] [diff] [review] patch v0 Remove the unnecessary seek, and the comment referring to the start attribute (which has been removed from the spec). Also removes some code from the Ogg decoder's seek which looks like a workaround for this problem. It's no longer necessary. It'd be good to get this fix in, since it can cause spurious test failures.
Pushed to mozilla-central: http://hg.mozilla.org/mozilla-central/rev/3611062ed098
This needs to land on 1.9.1 before bug 462570 can land on 1.9.1.
Pushed to mozilla-1.9.1: http://hg.mozilla.org/releases/mozilla-1.9.1/rev/ea80c6dfdd99