Interesting development, but even Chrome doesn’t support Dart by default.
Google’s Dart[2] language is now[3] an official ECMA standard with the catchy name of ECMA-408[4]. ECMA[5] may not be a household name, but if you’re reading this, your browser is using ECMAscript to render at least some parts of this page. That’s because ECMAscript[6] is the official standard body behind JavaScript. In the past, the organization has also been behind the specs for JSON, C#, the Office Open XML format and various CD-ROM specs.