Merge http://trac.webkit.org/changeset/167851 : Frame and page lifetime fixes in WebCore::createWindow
and http://trac.webkit.org/changeset/167790 : FrameLoader::checkCompleted can hit the "ref'ing while destroyed" assertion
and http://trac.webkit.org/changeset/167790 : FrameLoader::checkCompleted can hit the "ref'ing while destroyed" assertion