Written as a step toward converting Angular-Google-Chart to TypeScript, this definition file for the Google Charts API is available on it's own here.
I make no guarantee that this is 100% complete or accurate. I'm not accepting pull requests yet, but I will once I get together a Contributor's License Agreement and my own changes are stablized.
I release this definition file free for use under the MIT Open Source License, but keep in mind that the library these definitions are based upon is free, but privately licensed by Google under their own Terms of Service.