WebEngineView does not work inside a QQuickRenderControl

When using a QQuickRenderControl to render a QML UI to an OpenGL surface, WebEngineView items do not render properly. Diving into this problem it appears to be that WebEngineView wants to use a global OpenGL context created by QtWebEngine::initialize, but there is no public API for accessing that context in order to share it with the QQuickRenderControl context.

I've been able to work around the problem by manually creating a new offscreen context which is shared with my QQuickRenderControl and calling the non-public function qt_gl_set_global_share_context(), rather than calling QtWebEngine::initialize. This allows the WebEngineView to render properly.