Google Drive is now available for Chromebooks and Cr-48. It has been integrated with the File Manager Aura.
If you have not rebooted your system for a while you need to do that now in order to automatically update your Chromebook. Once updated you will not only see the brand new ChomeOS UI but will also notice the Drive in the File Manager.
Cr-48 users should switch to the dev-channel in order to get the new UI along with Aura file manager. The integartion of Drive brings additional 5GB of storage for Chromebooks.