System Information
Windows 7, GTX 1070 (Gigabyte)

Blender Version
Broken: 2.78b
Worked: 2.78

Short description of error
When 3D viewport is set as Material shaded, it appears to no longer display textures that are limited to show as Camera Ray only (Light Path node).
When muting the Light Path node, it goes back to normal. (check the pictures below)
Obs: There are no problems concerning the final render. It is viewport only.

Exact steps for others to reproduce the error
1- Set 3D Viewport shading as Material.
2- Uv unwrap a mesh and give it some image-based texture.
3- On cycles, give it a material.
4- Link the image texture to an emission node.
5- Link the emission node to the material output. Texture should display on 3D viewport.
6- Add a Light Path node and link the Is Camera Ray to the strength of the Emission node. Texture vanishes from viewport.