In order to record, upload or select videos from Gmail, you must have the Dubb Chrome Extension.

Once you have installed the Dubb Chrome Extension, you will see a small Dubb icon within your Gmail window.

From here you will be able to record, upload, or select videos directly from Gmail.
Here is a screenshot of the recording option:

Here is a screenshot of the "Select" functionality:

And here is a screenshot of the upload functionality:

Once you finish adding a video, it will automatically paste into the body of an email with an animated gif thumbnail and tracking capabilities. See below for a screenshot.