GitLab

Stop using HTTP/2 in case TLS 1.2 is not supported, connection has been
downgraded to below TLS 1.2, or AES-GCM cipher required by HTTP/2 draft
specification is not supported.

BUG=436835

Review URL: https://codereview.chromium.org/757033004

Cr-Commit-Position: refs/heads/master@{#308226}