Hi,
During Cornerstone development, we had disabled keyguard for convenience as we had to run many tests. If you want to enable keyguard, then go to WindowManagerService class and you can apply either of two solutions mentioned below.
1. In WindowManagerService() constructor method set enable keyguard to true.
mPolicy.enableKeyguard(true);
2. Just comment the below statement in WindowManagerService() constructor method.
//mPolicy.enableKeyguard(true);
After you make the above changes, build the ICS + Cornerstone code and deploy the newly built ROM to your device.
I hope the above info answers your query.
Thank you,
Sanjay Jain