[eme] Update to editor's draft for bugs 21155 and 21569

All,

I have made an update [1] to the Editor's Draft to propose a new section,
2.2, describing (non-normatively) the possible limits on the operation of
the Media Element when a CDM is used. This is to address bug 21155 [2],
which concerns restrictions on Javascript APIs that provide access to the
media data and 21569 [3] which addresses other restrictions, specifically
on rendering area.

Please re-open the bugs if you have comments on the proposal.

...Mark

[1] https://dvcs.w3.org/hg/html-media/rev/fc9e628b538f
[1] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21155
[2] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21569