x-google-ad-id of a device: the Google advertising id when the device has
one (hasGoogleAdId absent means it has, the devices with Google
Play Services), and undefined for a device without one (the Redroid
emulators), so the request builder omits the header instead of sending a
family id for it.
x-google-ad-idof a device: the Google advertising id when the device has one (hasGoogleAdIdabsent means it has, the devices with Google Play Services), andundefinedfor a device without one (the Redroid emulators), so the request builder omits the header instead of sending a family id for it.