Pointer Lock requestPointerLock rejects locking an element not in a document.

https://bugs.webkit.org/show_bug.cgi?id=90821

Reviewed by Adrienne Walker.

Source/WebCore:

Test: pointer-lock/lock-element-not-in-dom.html

* page/PointerLockController.cpp:
(WebCore::PointerLockController::requestPointerLock):

LayoutTests:

* pointer-lock/lock-element-not-in-dom-expected.txt: Added.
* pointer-lock/lock-element-not-in-dom.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@122169 268f45cc-cd09-0410-ab3c-d52691b4dbfc