The event targets of touch events are not necessarily to be the same as their corresponding pointer events. So we don't have to cache the event target of pointer events when they are generated from touch.
MozReview-Commit-ID: 9Gd6ion7NXf
Spec says we should throw an exception when setting pointer capture while the page has a locked element. Also, we should release all pointer capture when a pointer lock is successfully applied on an element.
MozReview-Commit-ID: CuUIPipJWB0
Revise the pointer event implementation, includes
- Revise the implementation to fetch preference values.
- Separate the logic to get the pointer capturing frame to PointerEventHandler.
MozReview-Commit-ID: 7pdAr0XFNT2
Stone Shih