We avoided fixing these because it causes changes in just about all of
the test data, which is annoying when reviewing or blaming changes.
But the previous several commits also caused changes in just about all
of the test data, so we might as well do this too.
Change-Id: I83b64d83b6f12c04dc06c0cadff7cdd89417e137
Our threads now also contain all replies to their sub-threads.
This is similar to how sections work in MediaWiki, where the parent
section also contains the content of all the lower-level sections.
We're going to need this for notifications about replies in a thread.
Bug: T264478
Change-Id: I241fc58e2088a7555942824b0f184ed21e3a8b6f
