Include an optional top origin in NetworkConnectionToWebProcess's Blob URL sets
<rdar://problem/111926766>
Pull request: https://github.com/WebKit/WebKit/pull/15649
Committed 266022@main (9fcb4920e2c1): <https://commits.webkit.org/266022@main> Reviewed commits have been landed. Closing PR #15649 and removing active labels.