Suppress mousedown and mouseup events that occur 300ms after the synthetic click event is fired, since they may confuse client code.   Also, do a better job of suppressing the native click event that (may) occur 300ms after the synthetic one; it sometimes appears on the DOMNode behind a popup that was closed in the 300ms interval.   Patch from Eric Durocher (IBM, CCLA).

Refs #15878 !strict.