Grab pass + VR is broken in Unity 2017

It looks like the grab pass only captures one of the 2 eyes in Unity 2017.

To illustrate this I made a simple project with SteamVR plugin 1.2.2 and Shader Forge.

In the scene I have the SteamVR Camera Rig prefab, a few boxes surrounding it and a Plane primitive with a material that has this simple shader on it:

Running this project on Unity 5.5.4p4 gave me this view of the Plane:

Running the same project on Unity 2017.2.0b11 gave me this:

As you can see, in 2017 we only see one eye (with some black bars) instead of both eyes.

Is this a Shader Forge bug or a Unity bug?