Reviewed by Maciej.

    Reviewed by Maciej.

        Cache the lastItem and lastItemOffset for fast retrieval of the
        same index or indeicies greater than lastItemOffset. Also cache
        the length. Like other node lists these cached values rest when the
        subtree under the root node changes.

        * khtml/xml/dom_nodeimpl.cpp:
        (ChildNodeListImpl::length): Use cachedLength when possible.
        (ChildNodeListImpl::item): Use lastItemOffset and lastItem if we can.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@11396 268f45cc-cd09-0410-ab3c-d52691b4dbfc