GitLab

This CL is split off rdsmith@'s CL at
https://chromium-review.googlesource.com/c/chromium/src/+/925181

This CL only adds the logging code for events, but uses a null NetLog.
A followup CL will modify the CookieStore constructor to pass in a non-null
NetLog.

Bug: 801910
Change-Id: Icd40aa206055c82a4e84ddb66c8547b69ec662ff
Reviewed-on: https://chromium-review.googlesource.com/1170594Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Commit-Queue: Helen Li <xunjieli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582603}