GitLab

This CL contains following changes:
1. TODO about cancelling pending subscriptions replaced with comment
explaining why current behavior is better.
2. Access token request backoff timer no longer resets on the first
successful request.

Bug: 1020117
Change-Id: I50930bdd5a998b41bd83525d88f5c525b34cd457
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2047107Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Maksim Moskvitin <mmoskvitin@google.com>
Cr-Commit-Position: refs/heads/master@{#740644}