passiveTouchGestures probably shouldn't apply to touchend

[RByers]

Touch scrolling is designed to be fast when touchstart and touchmove listeners are passive, but it's fine for touchend to be non-passive (since it doesn't block scrolling). See here for some details including:

Although it's still necessary to do so for mobile Safari, websites should not rely on calling preventDefault() inside of touchstart and touchmove listeners as this is no longer guaranteed to be honored in Chrome. Developers should apply the touch-action CSS property on elements where scrolling and zooming should be disabled to notify the browser before any touch events occur. To suppress the default behavior of a tap (such as the generation of a click event), call preventDefault() inside of a touchend listener.

From code inspection it looks to me like Polymer's passiveTouchGestures feature (#3604) sets all touch listeners to passive, including touchend. This will make adoption harder because it disables the ability to suppress click events. See for example b/66423965 inside Google.

Perhaps passiveTouchGestures can simply be updated to apply only to touchstart and touchmove listeners?

/cc @azakus @dtapuska

[dfreedm]

Ah, I missed this guidance somehow!
I'm totally fine making this change as it removes most of the tradeoffs, thanks!