[touch-events] explicitly define what happens with Touch Events during scrolling? (#60)

Perhaps just as an informative (non-normative) box-out, but: unless I'm missing it, the spec currently does not explicitly say whether or not `touchmove` is supposed to keep firing during scrolling, and whether or not `touchend` (and the compatibility mouse events + `click`) should fire once scrolling finishes.

This has historically been a grey area - for instance, Chrome used to fire `touchcancel` as soon as a scroll started (https://www.youtube.com/watch?v=h2djIdAFc5U#t=518), and there used to be further inconsistencies across browsers/OSs https://www.youtube.com/playlist?list=PLbPjl9UGMTycW_pCqnxCTHCy2MLl6HwDO

Most (?) browsers now seem to have settled on firing `touchmove` during scroll, and then `touchend` (but *no* mouse / `click` events) once scrolling finishes. Worth documenting this de-facto behavior? Even if prefaced with some wording that still leaves this up to individual implementations? Softened with a `MAY` or `SHOULD` ?

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/touch-events/issues/60