I'm Not There (1956) writes "Last week the news came in that Google is supposed to unveil 'Dart,' a new programming language for browser-based apps. Now an internal email from late last year describes this project as the 'high risk/high reward' path [of Google's browser development strategy]. Apps in this new language will run in a VM on browsers that support it, and can be translated to JS for other browsers. 'Performance, developer usability, and ability to be tooled' are the main characteristics of the language."
The email notes that Google will be working on ECMAScript Harmony
in the near term, but they describe the project as ultimately doomed by "fundamental problems" with ECMAScript. It's interesting that Google took part in abandoning ECMAScript 4, which would have been almost fully backward compatible
with current implementations while solving most of the "fundamental problems" Google claims require a brand new language to fix.