Pointer Lock: Change isLocked() from operator to attribute isLocked

https://bugs.webkit.org/show_bug.cgi?id=76311

Reviewed by Adam Barth.

Source/WebCore:

This patch implements the recent Mouse Lock Specification update
changing navigator.pointer.isLocked() to .isLocked.

Test pointer-lock/pointer-lock-api.html updated to new spec.

* page/PointerLock.idl:

LayoutTests:

* pointer-lock/pointer-lock-api-expected.txt:
* pointer-lock/pointer-lock-api.html:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105011 268f45cc-cd09-0410-ab3c-d52691b4dbfc