You have it backwards. There's no reason for browsers to choose CoffeeScript or TypeScript because they do not change the semantics of JavaScript which make it hard to optimize for. There really isn't anything for a browser to adopt with one of those languages, other than a small translation to JS.

Dart is fundamentally different in that it was designed for speed (as well as toolability and readability) and by directly supporting Dart a VM can make many more optimizations than a JS VM can. The Dart VM is already 1.5-2x faster than JS in some cases, while being _much_ younger.