[MSE] Spec updates published

I have posted more changes to the Media Source
Extensions<https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/media-source.html>
 spec.

Summary of changes:
- Added a note clarifying that the internal timestamp representation
doesn't have to be a double.(Bug
19676<https://www.w3.org/Bugs/Public/show_bug.cgi?id=19676>
)
- Added steps to the coded frame processing algorithm to remove old frames
when new ones overlap them.
- Fix isTypeSupported() return type.
- Clarify what top-level boxes to ignore for ISO-BMFF.(Bug
18933<https://www.w3.org/Bugs/Public/show_bug.cgi?id=18933>
)
- Add a check to avoid creating huge hidden gaps when out-of-order appends
occur w/o calling abort(). (Bug
18400<https://www.w3.org/Bugs/Public/show_bug.cgi?id=18400>
)

Diffs:
https://dvcs.w3.org/hg/html-media/rev/77975abeec41