Bypass call to String::substring() in HTMLConstructionSite::insertTextNode() in the common case.
Pull request: https://github.com/WebKit/WebKit/pull/3804
Committed 253961@main (d82c68599fe3): <https://commits.webkit.org/253961@main> Reviewed commits have been landed. Closing PR #3804 and removing active labels.
<rdar://problem/99352777>