https://bugs.webkit.org/show_bug.cgi?id=120344

Reviewed by Ryosuke Niwa.

This patch cleans ClassList and DOMSettableTokenList to make it simpler to update
SpaceSplitString:
- Move the implementation of virtual functions to the cpp file.
- Clean the #includes.
- Make the implemented pure virtual methods final.
- Make the element() accessor const.

* html/ClassList.cpp:
(WebCore::ClassList::create):
(WebCore::ClassList::element):
(WebCore::ClassList::value):
(WebCore::ClassList::setValue):
(WebCore::ClassList::classNames):
* html/ClassList.h:
* html/DOMSettableTokenList.cpp:
(WebCore::DOMSettableTokenList::create):
(WebCore::DOMSettableTokenList::ref):
(WebCore::DOMSettableTokenList::deref):
(WebCore::DOMSettableTokenList::length):
(WebCore::DOMSettableTokenList::value):
* html/DOMSettableTokenList.h:
* html/DOMTokenList.h:
(WebCore::DOMTokenList::element):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154707 268f45cc-cd09-0410-ab3c-d52691b4dbfc