Today Google announced the integration of Google Drive and Gmail. In that update you can view and save files directly to Google Drive without actually having to leave Gmail.
When you receive an file attached email, you’ll see previews of the files at the bottom of the message. When you click them, you’ll get full-screen views of the images/documents. You can then read, search or browse through them from Gmail itself.
By clicking the Drive button you can now save your attachments directly to Drive
