function traverseTwoPhase(inst, fn, arg) {
	  var path = [];
	  while (inst) {
	    path.push(inst);
	    inst = inst._hostParent;
	  }
	  var i;
	  for (i = path.length; i-- > 0;) {
	    fn(path[i], 'captured', arg);
	  }
	  for (i = 0; i < path.length; i++) {
	    fn(path[i], 'bubbled', arg);
	  }
	}
Simulates the traversal of a two-phase, capture/bubble event dispatch.