Remove WebCore::Node::isActiveNode() since it isn't called anywhere.
https://bugs.webkit.org/show_bug.cgi?id=111646

Reviewed by Kentaro Hara.

No new tests. This removes dead code.

* dom/Node.h:
(Node):
* html/HTMLAudioElement.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145021 268f45cc-cd09-0410-ab3c-d52691b4dbfc