This is very noisy (logs several times in the same request), but
I'm not sure much can be done about that. It is a flaw in
SessionManager, which does call SessionProvider::persist/unpersist
that many times, and relies on cookie deduplication in WebResponse.
But it should give some idea of when cookies are emitted, and does
not log on normal requests (where no cookies are emitted) so it
shouldn't overload the logging backend.
Bug: T264793
Change-Id: I93733d73af1dfcf539a94b17cf5e4de76cc59748
a6cdedad8d