When using python offscreen rendering the background was not drawn in EEVEE. Users would expect that when calling the `draw_view3d` method that it shows the same as in the 3d viewport. Seems to be a difference between the meaning of draw_background in b279 and b280. In B279 the world background would be drawn. In B280 the transparency is changed. Reviewed By: campbellbarton, fclem Maniphest Tasks: T61768 Differential Revision: https://developer.blender.org/D5022