In the investigation in bug 889220, I found that up to 3% of user-initiated navigations come from clicking the tiles on the New Tab Page on desktop, and up to 3% of user-initiated navigations on Android come from clicking the most visited tiles. These should pass the timestamp of the input event through to CommonNavigationParams so that they are tracked in InputToFirstContentfulPaint metrics.

Tom, do you think you'd be able to take this?