NoCache sent `no-cache, no-store, max-age=0, must-revalidate, value`. The
trailing `, value` is not a directive; it is a leftover token that has been on
every response this middleware touches since the file was written. Unknown
directives are ignored, so nothing misbehaved because of it, but it went out on
the wire and read as a mistake to anyone looking.
The assertion added in #937 pins the old value, so it moves with the source:
removing the token from the middleware alone turns TestNoCache red, which is
the whole point of that test and the reason both lines change together here.
zhangwenjian