It's more efficient to connect body to the document before invoking tryFastParsingHTMLFragment since that'll avoid secondary insertedIntoAncestor traversal on the newly created subtree.
Pull request: https://github.com/WebKit/WebKit/pull/24129
Committed 274429@main (2652615cd5bd): <https://commits.webkit.org/274429@main> Reviewed commits have been landed. Closing PR #24129 and removing active labels.
<rdar://problem/122720540>