GitLab

Add method to ServiceDiscoveryClient that will allow it to actively refresh
stale services when their TTL runs out.

BUG=336883

Review URL: https://codereview.chromium.org/141583010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247857 0039d316-1c4b-4281-b951-d872f2087c98