Remove ContainerNode overload for NodeTraversal::nextSkippingChildren()

Remove ContainerNode overload for NodeTraversal::nextSkippingChildren() as it
adds no benefit compared to the one taking a Node in argument.

The nextSkippingChildren() implementation does not involves visiting the
children (and thus calling firstChild() / lastChild()). Therefore, there is no
benefit to knowing that the argument is a ContainerNode (unlike for
NodeTraversal::next()).

This CL also does the same for ElementTraversal::nextSkippingChildren().

R=esprehn@chromium.org, adamk@chromium.org

Review URL: https://codereview.chromium.org/420603012

git-svn-id: svn://svn.chromium.org/blink/trunk@179055 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Get rid of unnecessary isChildNodeList() virtual call in clearChildNodeListCache()

This CL inlines clearChildNodeListCache() in the caller as there is only one to
avoid an unnecessary isChildNodeList() virtual call. The calling method is
invalidateNodeListCachesInAncestors(), which this CL moves from Node to
ContainerNode to make sure it is only called for ContainerNodes (Only
ContainerNodes' node lists have caches that need invalidation).

R=adamk@chromium.org, esprehn@chromium.org

Review URL: https://codereview.chromium.org/413763004

git-svn-id: svn://svn.chromium.org/blink/trunk@179056 bbb929c8-8fbe-4397-9dbb-9b2b20218538