Spec change https://github.com/w3c/media-source/pull/154 is expected to land soon. Chrome is already not compliant with either the before or after #154 state. Assuming #154 lands, Chrome MSE needs:

* updated endOfStream behavior around calculation of highest end time (using highest track buffer range end time, not highest intersected track buffer range (SourceBuffer.buffered) end time, across all SourceBuffers.
* updated duration change algorithm behavior, which "bumps up" the desired duration to a similarly calculated highest end time.
* test that:
1) If current duration is D, highest track buffer range end time E<D:
 a) setting duration attribute to D is no-op (with no 'durationchange')
 b) setting duration attribute to E results with duration==E and 'durationchange' event enqueued
 c) setting duration attribute to X<E, X > highest buffered PTS, results with duration==E and 'durationchange' fired
2) If current duration is D, highest track buffer range end time E==D:
 a) setting duration attribute to D is no-op (with no 'durationchange')
 b) setting duration attribute to X < D, X > highest buffered PTS, results with duration "bumped back up" to D *and* 'durationchange' event fired

Note: 1c and 2b are different than before #154 and also different than current Chromium implementation.

Note also that the current capping of the highest buffered range end time to be duration *should* be unnecessary once implementation matching #154 lands in Chromium; suggest that such capping be replaced with DCHECKs.