* Add back launch screen view until first frame on iOS
* improvements
* Move callback plumbing from ios surfaces to the gpu rasterizer. Didn’t wire java JNI yet.
* Android JNI
* Fix ios reference count and let android engine manage a view on top with launch screen
* Hook up Android activity and view
* review notes
* review notes
* Move thread switching upstream. Use weak references for callbacks.
* Some clean up