GitLab

This change adds a separate class to do the dirty work of running and
retrying a task if it fails. This will be used for all tasks that would
need to be run on an update check.

BUG=924762
TEST=Unit tests.

Change-Id: I89cc65fc93631989857c3bd8dce6f53dca31fe2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1661972Reviewed-by: Pavol Marko <pmarko@chromium.org>
Commit-Queue: Abhishek Bhardwaj <abhishekbh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671479}