Re-enable web font CORS failures histogram

r175927 removed histogram counting for web font CORS failures
but we want to keep counting for a while.

BUG=286681

Review URL: https://codereview.chromium.org/336173006

git-svn-id: svn://svn.chromium.org/blink/trunk@177272 bbb929c8-8fbe-4397-9dbb-9b2b20218538