Only the “Instant Preview” of GoogleVR repository. Does not support controllers.
The GoogleVR plugin has a bunch of important things, but it gets quite blotaed at times, with all the code for Daydream, iOS and their custom raycasting for Unity UI interactions among other things.
I personally prefer to use a slightly modified version of Unity VR Standard Assets and only require GoogleVR for their great Instant Preview feature.
This repository strips everything away from GoogleVR except InstantPreview.