This experiment has been disabled for everyone for a while: if we
bring something like this back, it is not likely to be exactly the same,
and will be different enough to require a different implementation.
As it is, the summarization code was making a few code paths (rendering
especially) more complex, and is worth removing for simplicity's sake.
(imported from commit 6ac8cdc9f7077a5a1da01ab4268aba3db0bc43f8)
Rafid Aslam
Ashish
Zev Benjamin
Leo Franchi
Tim Abbott