The issue here was that the Barbershop benchmark scene was saved with a
custom OCIO config, which leads to some textures having a unknown
colorspace when loading with a default installation.
This is automatically fixed by Blender during image loading, but since
Cycles queried the colorspace before actually loading the image, it
didn't get the updated value in the first render.
To fix this, just re-query the colorspace after the image is loaded.
Note that non-packed images still get treated as raw data if the
colorspace is unknown, but this is at least consistent and doesn't
magically change when you press F12 a second time.
Differential Revision: https://developer.blender.org/D16427
1c27cc5529