I don't know what an accessible media source is
Can't synchronize everything without magic
Merge pull request #63 from martinthomson/syncfromdifferentclocks

Clarify in section 4.1 that synchronization is only an intention because some tracks cannot be synchronized.
updated change log
Merge pull request #62 from martinthomson/constructedfromwat

"accessible media sources" changed to "existing media streams or tracks"
Fixed enabled/disabled mixup
Space after period
Replace spaces before commas due to line breaks

perl -0 -pi.0 -e 's!(\n\s+)(</code)(>,)!!msg'
try to markup dB SPL
Spelling: cannot
Spelling: exactly
Spelling: interface
Spelling: limitations
Spelling: possible
Spelling: satisfied
Spelling: with
ED: intro
RFC: must in conformance (WebIDL) -- maybe
RFC: must not in Terminology-source
significant meaning: released/exposed in Terminology-source