"Extra steps for Cordova/PhoneGap Build
Google Play Game Services are designed to work in a web browser, but it's possible to also configure it to work in a web view, such as when building a mobile app with PhoneGap Build. To set it up for Cordova you'll also need to:
Fill in the Client secret property with the value from the Google Play Developer Console.
Add as one of the redirect URIs in the API console.
Remove any uses of On auto-sign in failed. It never triggers in this mode, so you will need to rely on having manual sign-in instead."
Unfortunately at this time Google Play Game Services only work from a web browser. It does not currently work from Crosswalk or any non-browser wrappers like CocoonJS or Ejecta. However it should still work on mobile browsers such as Chrome for Android."
Due to the recent "one cordova exporter" thing, I would guess that crosswalk would be compatible with it the same way cordova and phonegap build are, if that is not the case however, it would be nice to add a little precision in the extra steps for cordova builds to say "crosswalk does not rely on the device webview to work, so unfortunatelly that feature cannot be used" (or whatever explanation it is in reality).