This will be useful to let the MediaCache flush its block cache without having
to restart from scratch (and risk failing).
MozReview-Commit-ID: At3mxH9jb9m
--HG--
extra : rebase_source : b5ac513c6d6d100c8eb41220991388470c0b1a5e
The only external use of Close was always followed by an implicit destruction
(by resetting the RefPtr), so we don't need to expose it, and it can be done
from the destructor.
FileBlockCache keeps its Close() function for internal use.
Also, FileBlockCache::mIsOpen is redundant, as it's true iff mThread is not
null.
MozReview-Commit-ID: LV7YVrwJvGG
--HG--
extra : rebase_source : 23decadf249b9e63190b3e19d81edc4a090afcef