auto exclude non selected layers from render when lock camera and layers is deselected in the 3d view.

I noticed that if I press f12 to render when 'lock camera and layers' icon is deselected in the 3d viewport, that only the active layer is rendered...which is great. The only problem is that all of the non-active layers still get calculated.

It would really speed up test renders if all non active layers in the 3d viewport were not calculated (much like if you use the exclude buttons in the render layers tab with 'lock camera and layers' enabled.

I need this functionality the most when I want to quickly render full particle systems that the 3d viewport can't handle if display is set to 100%.