@OwnerUser public String getDeviceOwner() {
		if (! Hacks.DevicePolicyManager_getDeviceOwner.isAbsent()) {
			return Hacks.DevicePolicyManager_getDeviceOwner.invoke().on(getManager());
		} else if (isActiveDeviceOwner()) return sCachedComponent.getPackageName();        // Fall-back check, only if we are the device owner.
		else return "";
	}
@return the package name of current device owner, null if none or empty string if unknown.
shared/src/main/java/com/oasisfeng/island/util/DevicePolicies.java