So in testing this morning, it appears the ability to share a link to a Google Drive file has not yet been implemented in the Android app like it can be done from the Dropbox app. As a work around, you can "send" the file from Drive to Dropbox on your Android device, and then share the link from Dropbox. Yes, it's a little work but can get you out of a jam if needed.
Right now all you can do is send the file to email from the Google Drive app.
Right now all you can do is send the file to email from the Google Drive app.