Currently experiencing an issue when re-entering Google Daydream game after exiting the Daydream setup (place your phone in headset) screen by pressing the x in the top left corner of the screen. When the game is booted back up again sporadically just being presented by a completely black screen - the screen divider line is not even showing up.
(Was observed on both Pixel and Pixel XL)
Can be reproduced with attached project.
This has been observed in a project with no special blueprints or settings, other than the absolute basics of an unreal google daydream project, as outlined here: https://docs.unrealengine.com/latest/INT/Platforms/GoogleVR/QuickStart/index.html
Also reproducible by pressing the x while app is running and attempting to relaunch(resume?) with app switcher.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-46640 in the post.