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