GitLab

Canary connection attempts occur on network changes, and are capable of
bypassing backoff (without resetting it). As such they happen immediately
if no connection attempt is already in progress, but if they fail backoff
will be increased accordingly.

BUG=355126
R=asvitkine@chromium.org, jianli@chromium.org

Review URL: https://codereview.chromium.org/213693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260308 0039d316-1c4b-4281-b951-d872f2087c98