//var chx = this.getChildAt(0)
//var chy = this.getChildAt(1)
//var chz = this.getChildAt(2)
//this.numChildren
3
//this.addChildAt(chx, 0)
//chx === this.getChildAt(0)
true
//chy === this.getChildAt(1)
true
//chz === this.getChildAt(2)
true
//this.numChildren
3
//Removed symbol "chx" in timeline
//chx === this.getChildAt(0)
true
//chy === this.getChildAt(1)
true
//chz === this.getChildAt(2)
true
//this.numChildren
3
//Inserted "chx"'s symbol at same depth in timeline
//chx === this.getChildAt(0)
true
//chx === this.getChildAt(1)
false
//chy === this.getChildAt(2)
true
//chz === this.getChildAt(3)
true
//this.numChildren
4
