Max write buffer size for an idle connection. When we place an idle
Connection into connectionStack_ or on every resizeBufferEveryN_ calls,
we ensure that its write buffer is <= to this size; otherwise we
replace it with a new one of writeBufferDefaultSize_ bytes to ensure that
idle connections don't hog memory. 0 disables this check.
Max write buffer size for an idle connection. When we place an idle Connection into connectionStack_ or on every resizeBufferEveryN_ calls, we ensure that its write buffer is <= to this size; otherwise we replace it with a new one of writeBufferDefaultSize_ bytes to ensure that idle connections don't hog memory. 0 disables this check.