Google developed a Chrome extension for Google Scribe text completion service. By default, Google Scribe is disabled, but you can enable it by pressing Ctrl+J. You can also press Ctrl+Shift+J to switch to on-demand mode that shows suggestions only when you press Tab. If you find Google Scribe useful or you use the on-demand mode, there's an option to automatically activate the service for any text field.
In the screenshot below shows some new Gmail features that're currently tested internally at Google: inserting Google Docs files, photos and maps.
Download: Chrome Extension