- Correctly handle upstream surface region size changes. Test and debug
  set_render_rect
- Make sure we are considering DAR on all scaling/rendering cases
- Test and debug caps renegotiation
- Drop android specifics like the default window h/w
- Move EGL/GLES context to it's own struct. Proly move GLSL stuff to it's
  own header too
- Optimize shading routines if possible.
- Either finish implementing or drop fast rendering path logic
- Implement buffer pool
- Finish code documentation