Upgrading Android app to latest Unity & Google VR now says "app has stopped"

After upgrading an existing Android game to Unity 5.6.1p3 with Google VR SDK 1.60, I now get an immediate crash "Unfortunately, app has stopped" message. I opened Android Studio and looked in the logcat window:

06-13 14:21:43.624 293-3659/? E/AudioPolicyManager: unknown stream type
06-13 14:21:43.624 293-3659/? E/AudioPolicyManager: unknown stream type
06-13 14:21:43.634 29546-29546/? E/AndroidRuntime: FATAL EXCEPTION: main
Process:...

Upgrading Android app to latest Unity & Google VR now says "app has stopped"