When a last child node is an insertion point which does not have distributed nodes nor fallback elements, ComposedShadowTreeWalker::lastChild should ignore such a insertion point. Currently, walker.get() wrongly returns null after walker.lastChild() is called in such case.
Created attachment 153739 [details] Skip empty insertion points and continue walking
Created attachment 153742 [details] Patch for landing
Comment on attachment 153742 [details] Patch for landing Clearing flags on attachment: 153742 Committed r123312: <http://trac.webkit.org/changeset/123312>
All reviewed patches have been landed. Closing bug.