[MSE] Spec Updates Published

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

Summary of changes:
Bug 25347 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=25347> - Remove
unnecessary null & invalid enum value checks.
Bug 25505 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=25505> - Introduce
"generate timestamps flag" to handle MPEG audio timestamp generation.

Diffs:
https://dvcs.w3.org/hg/html-media/rev/ba5233c6654d
https://dvcs.w3.org/hg/html-media/rev/29f17705b5c2

Aaron