Executes the final stage of batch rendering - drawing. The drawer can assume that
all display-objects have been into the batch-factory and the batch-geometry factory.
This method will be called after all display-object have been fed into the
batch and batch-geometry factories.
Hint: You will call some form of BatchGeometryFactory#build; be sure to release
that geometry for reuse in next render pass via BatchGeometryFactory#release(geom).