Re: hasOwnProperty('touches') for differentiating a TouchEvent from a MouseEvent

[Trying again to get the pain-text code snippet formatted correctly in the
archives (sorry for the spam)]

Here's a funny pattern we just noticed
<https://code.google.com/p/chromium/issues/detail?id=474436#c12> for code
attempting to handle both touch and mouse events with the same code:

getPointerPosition = function(j) {
  if (j.hasOwnProperty("touches")) {
    return {x: j.changedTouches[0].pageX,y: j.changedTouches[0].pageY} }
  else {
    return {x: j.pageX,y: j.pageY} } }
 ...
g._onPointerDown = function(k) {
  if (!k.hasOwnProperty("touches")) {
    k.preventDefault()
  }
  this.mouse = h.getPointerPosition(k);
  this.prevMouse = {x: this.mouse.x,y: this.mouse.y};
  this._isDragging = true;
  this._onWillBeginTracking();
  document.addEventListener("mousemove",
this._boundFunctions.onPointerDrag, false);
  document.addEventListener("touchmove",
this._boundFunctions.onPointerDrag, false);
  document.addEventListener("mouseup", this._boundFunctions.onPointerUp,
false);
  document.addEventListener("touchend", this._boundFunctions.onPointerUp,
false);
  document.addEventListener("touchcancel",
this._boundFunctions.onPointerUp, false)
};

This used to work to identify TouchEvents in Chrome (and Safari) due a
longstanding bug <https://code.google.com/p/chromium/issues/detail?id=43394>
where DOM attributes were incorrectly exposed on the instance
<https://docs.google.com/document/d/1yeHTCHhulVIlrKyx9_gCguAhLfcefVOa9uxxfW2LVG0/edit>,
instead of on the prototype chain (as required by WebIDL
<http://heycam.github.io/webidl/#es-operations>). The code should really be
using '"touches" in j' instead of using hasOwnProperty here.

Ironically, the site that has this code attempting (but failing) to handle
mouse and touch events with the same event handlers:
http://www.apple.com/watch/gallery/

We're trying to ship our fix for the DOM attributes bug now (but may resort
to a temporary compat hack to avoid breaking such sites). I assume such
pages are be broken on IE and Firefox (which have correctly implementing
DOM attributes on the prototype chain for some time), right? Have folks
seen other sites with this problem (searching github I see this pattern in
a few places)?

Rick