third_party/polymer3/bower_components/polymer/lib/utils/gestures.js
function PASSIVE_TOUCH(eventName) {
  if (isMouseEvent(eventName) || eventName === 'touchend') {
    return;
  }
  if (HAS_NATIVE_TA && SUPPORTS_PASSIVE && passiveTouchGestures) {
    return {passive: true};
  } else {
    return;
  }
}
function PASSIVE_TOUCH(eventName) {
  if (isMouseEvent(eventName) || eventName === 'touchend') {
    return;
  }
  if (HAS_NATIVE_TA && SUPPORTS_PASSIVE && passiveTouchGestures) {
    return {passive: true};
  } else {
    return;
  }
}
function PASSIVE_TOUCH ( eventName ) { if ( isMouseEvent ( eventName ) || eventName === 'touchend' ) { return ; } if ( HAS_NATIVE_TA && SUPPORTS_PASSIVE && passiveTouchGestures ) { return { passive : true } ; } else { return ; } }
Generate settings for event listeners, dependant on `passiveTouchGestures`

@param {string} eventName Event name to determine if `{passive}` option is
needed
@return {{passive: boolean} | undefined} Options to use for addEventListener
and removeEventListener
Generate settings for event listeners dependant on passiveTouchGestures