Steps to repro:

1. Open Unity;
2. Open attached project and 'test' scene;
3. Notice that there are 5 cubes in the scene, 4 of them (colored are using instanced shader) and one (white) is using standart shader;
4. Open Frame Debugger (Window -> Frame Debugger);
5. Click Enable;
6. Find 'Draw Mesh (instanced)' call and select it;

7. Notice that the preview is not shown for instanced mesh (see attached actual.png screenshot);
8. Find 'Draw Mesh Cube (4)' call and select it;

9. Notice that the preview is shown - expected result (see attached expected.png screenshot).

Notes:
- Reproducible in 5.5.0a1 and in 5.4.0b23;
- Reproducible on both OSX 10.11.4 and Windows 10.