Move needsPreviewElement to TimelineUIUtilsImple and make it private

Drive-by: removed formatter for counters field which is not in the protocol anymore.

BUG=361045
R=loislo@chromium.org

Review URL: https://codereview.chromium.org/343613004

git-svn-id: svn://svn.chromium.org/blink/trunk@176495 bbb929c8-8fbe-4397-9dbb-9b2b20218538