f155020465
ClientDirectoryLock::Id() is currently safe to call off the owning thread because it only accesses a const member. However, for consistency with other quota clients and in preparation for an upcoming change to use ClientDirectoryLockHandle (which enforces owning-thread access), this patch avoids off-thread access to the directory lock directly. Instead, we extract and cache the lock id on the owning thread immediately after acquiring the lock, and store it for later use off the owning thread. Differential Revision: https://phabricator.services.mozilla.com/D243655