Remove DOMSettableTokenList's overload of add() and remove()
https://bugs.webkit.org/show_bug.cgi?id=120341

Reviewed by Ryosuke Niwa.

Little refactoring to make other cleanups easier. Instead of modifying
SpaceSplitString directly, rely on DOMTokenList ultimately changing
the value, which in turn updates the tokens.

* html/DOMSettableTokenList.cpp:
* html/DOMSettableTokenList.h:
* html/DOMTokenList.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154667 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Unreviewed. Fix GTK+ build after r154601.

* TestWebKitAPI/GNUmakefile.am: Remove mac specific file from
compilation added by mistake in r154601.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154668 268f45cc-cd09-0410-ab3c-d52691b4dbfc