Expand classList test to cover exception in toString

Expand classList test to cover exception in toString
https://bugs.webkit.org/show_bug.cgi?id=120444

Reviewed by Benjamin Poulain.

Merge https://chromium.googlesource.com/chromium/blink/+/825fefb837133d5545964c17f6aa4b62bfe3df0c

When add and remove is called and there is an exception being thrown
in one of the arguments we need to ensure that we are not calling the
implementation of add and remove.

* fast/dom/HTMLElement/class-list-expected.txt:
* fast/dom/HTMLElement/class-list-quirks-expected.txt:
* fast/dom/HTMLElement/script-tests/class-list.js:
(shouldBeEqualToString):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@154799 268f45cc-cd09-0410-ab3c-d52691b4dbfc