UseCounter should exclude chrome-only feature usage (e.g. chrome://, chrome-devtools:// URLs). Currently Blink-side UseCounter (to be deprecated) is tracking NTP activities and browser-side UseCounter is not. To verify that browser-side UseCounter is behaving similarly to the blink-side UseCounter (so that it can replace the blink-side one), drop NTP activities in blink-side UseCounter.
Comment 1 by cha...@chromium.org
, Sep 8 2017