Add a Layout test for r188991

Add a Layout test for r188991
https://bugs.webkit.org/show_bug.cgi?id=148507

Reviewed by Tim Horton.

Tests that stopping an animation early and closing the window does
not crash the process. This is a retrospective test added for
https://bugs.webkit.org/show_bug.cgi?id=148442, "Fix crash due to
animationDidEnd called on deallocated RemoteLayerTreeHost."

* animations/crash-on-removing-animation.html: Added.
* animations/crash-on-removing-animation-expected.txt: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@189022 268f45cc-cd09-0410-ab3c-d52691b4dbfc