Resize Launcher in Unity 2D

I twittered about the memory usage is fat in Unity 3D. Although my T410 works fine. I still want to try to switch to Unity 2D. After that, the default icon in launcher is too large (48×48) as in Unity 3D. But the rezise bar in Appearance is gone. 

See the reference post for how to do it.

Reference: How to resize Launcher in Unity 2D.