Remove UserGesture on touch scrolls

The only type of touch which now takes a user gesture is touchend/pointerup
when it doesn't correspond to a touch scroll.  Conceptually scrolling
consume's the user's intent - no sensitive action should be triggered for
the same gesture that does a scroll.  For details see:

Intent to remove:!searchin/blink-dev/gesture%7Csort:relevance/blink-dev/TO_x7FRkdmw/uCrOwufTCAAJ


Cr-Commit-Position: refs/heads/master@{#430330}
16 files changed