Optimize HTMLToken::appendToAttributeValue() by appending all characters at once instead of one by one.
Pull request: https://github.com/WebKit/WebKit/pull/1279
Committed r295247 (251296@main): <https://commits.webkit.org/251296@main> Reviewed commits have been landed. Closing PR #1279 and removing active labels.
<rdar://problem/94371547>