WebEngineView poor quality when rendered via QQuickRenderControl

Text in a QML WebEngineView looks terrible when rendered via a QQuickRenderControl.

See webengine-window.png attachment for a screenshot of WebEngineView rendered in a window which looks good. See webengine-rendercontrol.png for the same rendered via QQuickRenderControl. The QML text looks good but the WebEngineView text does not.

The attached webenginerender.zip sample project renders multiple times because there seems to be no way to detect when the WebEngineView has actually drawn pixels, so we render a few times until it probably has.