Reviewed by Kevin.

    Reviewed by Kevin.

	<rdar://problem/3878766> VIP: Program listings pages at directv.com takes 75% of time traversing NodeLists

        * khtml/dom/dom_node.cpp:
        (NodeList::itemById): New method, just forward to impl.
        * khtml/dom/dom_node.h: Prototype it.
        * khtml/ecma/kjs_dom.cpp:
        (DOMNodeList::tryGet): Instead of looping over the whole list to do by-id access,
	let the NodeList do it. The NodeList might be able to do it more efficiently.
        * khtml/xml/dom_nodeimpl.cpp:
	(NodeListImpl::itemById): Optimize for the case where the NodeList
	covers the whole document. In this case, just use getElementById,
	then check that the element satisfies the list criteria.
        (ChildNodeListImpl::nodeMatches): Return true only if the node is our child.
        (TagNodeListImpl::TagNodeListImpl): Irrelevant change to reformat initializers.
        * khtml/xml/dom_nodeimpl.h:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8001 268f45cc-cd09-0410-ab3c-d52691b4dbfc