Stop using a raw pointer for Node::m_treeScope.
Pull request: https://github.com/WebKit/WebKit/pull/18326
<rdar://problem/116501041>
Pull request: https://github.com/WebKit/WebKit/pull/19418
Committed 269692@main (2714943f80da): <https://commits.webkit.org/269692@main> Reviewed commits have been landed. Closing PR #19418 and removing active labels.