This bug is in reference to the test at http://w3c-test.org/html/tests/submission/Opera/media/interfaces/TextTrack/cues.html. I think the error is on line 65:

    t1.cues[1].startTime = 0.5; // this should change it back

I think the wrong index is being changed here, it should now be the cue at in 0 since we'd just changed the order of the cues on line 62. I believe this would be the correct test:

test(function(){
    t1.mode = 'showing';
    t1.cues[1].startTime = 0; // this should change the text track cue order
    assert_equals(t1.cues[0].id, 'id2');
    assert_equals(t1.cues[1].id, 'id');
    t1.cues[0].startTime = 0.5; // this should change it back
    assert_equals(t1.cues[0].id, 'id');
    assert_equals(t1.cues[1].id, 'id2');
}, document.title+', changing order');

Note that another issue was reported for the same test at I've also filed a bug on the same test but for a different issue at https://www.w3.org/Bugs/Public/show_bug.cgi?id=20066.