The steps in this article will prevent the screen from dimming in a short time and it will keep the WiFi alive and connected when the lid is closed thus saving you a ton of time if you need your WiFi to survive all day.
First, switch to developer mode using the toggle switch on your device and reboot.
Second, when you see the scary warning at boot press CTRL-D. Use CTL-D on future boots to enter the developer mode. Note that any customization of chrome will be erased but when you log in to your account again you will get everything back since it is all in the cloud.
In developer mode: CTRL-ALT-T and enter these commands ...
cronos@localhost / $ sudo initctl stop powerd
That should do it. Sleep mode has been disabled.