GitLab

Removing an old UMA prefix as per crbug.com/390221.

BUG=390221
TEST=None

Review URL: https://codereview.chromium.org/395983005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287848 0039d316-1c4b-4281-b951-d872f2087c98