Add histograms to understand more about QUIC connection duration.

Change-Id: I498e2f963f28f83ba3e90822d45b25d2af98c525
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354837


Commit-Queue: Renjie Tang <renjietang@chromium.org>
Reviewed-by: David Schinazi <dschinazi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798339}