DecoderDoctorLogger and its related classes offer a cheap way to gather log
messages from media stack objects, and then process these messages to extract
object lifetimes and messages related to separate HTMLMediaElement's.
MozReview-Commit-ID: AIf2nAMjoDy
--HG--
extra : rebase_source : cf10185538aded870b9005e88563751f3638ae65
Gerald Squelart