This is for a few reasons:
* The leak logging isn't as useful as other types of logging, as
nsTArray_base is frequently relocated without invoking a constructor,
such as when stored within another nsTArray. This means that
XPCOM_MEM_LOG_CLASSES cannot be used to identify specific leaks of
nsTArray objects.
* The nsTArray type is layout compatible with the ThinVec crate with the
correct flags, and ThinVec does not currently perform leak logging.
This means that if a large number of arrays are transferred between rust
and C++ code using ThinVec, for example within another ThinVec, they
will not be logged correctly and might appear as e.g. negative leaks.
* Leaks which have been found thanks to the leak logging added by this
type have often not been significant, and/or have needed to be
circumvented using some other mechanism. Most leaks found with this type
in them also include other types which will continue to be tracked.
Differential Revision: https://phabricator.services.mozilla.com/D115087
407423d88c