There is now a new user interface for all of the pickers in Google Drive (the dialog that lets you select files or other content, e.g. Open files, Insert Images from Drive, etc).
The new interface conforms more closely with the new Google Drive UI. All of the menu options previously housed in vertical tabs on the left hand side of the dialog are moved to horizontal tabs placed along the top:
Release track is Rapid release and Scheduled release with gradual rollout.