Threads on a document, newest thread first, each with its replies oldest
first.
undefined until the first snapshot arrives. A thread's status and
fieldPath come from its first comment, so filtering by either selects whole
threads rather than individual replies.
Threads on a document, newest thread first, each with its replies oldest first.
undefineduntil the first snapshot arrives. A thread'sstatusandfieldPathcome from its first comment, so filtering by either selects whole threads rather than individual replies.