WebViewImpl::isUsingUISideCompositing() gets called before we've created a DrawingAreaProxy, so returns false then. In order to use the new WKScrollView/WKContentView code path, we need it to give an accurate result.
Pull request: https://github.com/WebKit/WebKit/pull/3273
Committed 253417@main (1dfe5d397bd9): <https://commits.webkit.org/253417@main> Reviewed commits have been landed. Closing PR #3273 and removing active labels.
<rdar://problem/98653866>