No longer allow opening pop-ups (and other sensitive operations) to occur during input events which represent a touch scroll. In particular, touchstart and touchmove listeners now never have a user gesture. touchend listeners do have a user gesture unless the user was scrolling / pinching. Builds on https://www.chromestatus.com/feature/5649871251963904.
Docs: https://github.com/WICG/interventions/issues/13 https://docs.google.com/document/d/1oF1T3O7_E4t1PYHV6gyCwHxOi3ystm0eSL5xZu7nvOg/edit
Samples: http://output.jsbin.com/kibaxu