Errors on import GoogleVRForUnity package on Unity 5.6.0b7

I’m using Unity 5.6.0b7 and the latest version of GoogleVRForUnity.unitypackage downloaded from the official website.

I receive all this errors from Assets/GoogleVR/Scripts/Controller/Internal/Emulator/PhoneEvent.cs after importing the package, and it can’t be cleared so I can’t play my scene.

Looks like you are missing Google.ProtocolBuffers.dll in Assets/Plugins, which should be included in the .unitypackage.