Android web views don't work in QML rendered offscreen via QQuickRenderControl

When attempting to rendering QML to an OpenGL texture on android, use of WebView elements do not end up rendered as part of the texture.

Based on inspection of the Java and JNI code in the WebView source, it looks as if such views are implemented using some kind of view compositing at the android level, after the entire QML scene has been rendered using OpenGL, rather than attempting to render the Android WebView to an offscreen surface of its own and rendering the resulting texture as part of the conventional QML scenegraph render.

This is a huge limitation for us.  Our application is primarily VR based and on desktop platforms the ability to use the QtWebEngine module to render HTML to an offscreen surface allows us to make HTML UIs available inside a 3D rendered VR environment.  However, we're starting to do more work with Android based VR headsets and so this issue is a giant missing feature.

Rendering an arbitrary Android view to an OpenGL texture is apparently a solved problem:  http://www.felixjones.co.uk/neo%20website/Android_View/