Adopt more smart pointers in WebCore/bindings.
Pull request: https://github.com/WebKit/WebKit/pull/24420
Committed 274647@main (cce92d99566e): <https://commits.webkit.org/274647@main> Reviewed commits have been landed. Closing PR #24420 and removing active labels.
<rdar://problem/122963901>
Re-opened since this is blocked by bug 269540