GitLab

Responding to wez@'s comments in crrev.com/2281323002.

This change removes a BackoffEntry for a component extension if it has loaded and there has been no additional failures for that extension within 60s.

BUG=639104

Review-Url: https://codereview.chromium.org/2310463002
Cr-Commit-Position: refs/heads/master@{#417315}