While Dart has always compiled to JS, TypeScript has always been "JS with types." Any JS file is a valid TS file if you change the filetype from .js to .ts but Dart has always been its own thing. I don't think Dart was ever natively supported in Chrome; there was a development fork of Chrome in which it was supported but it was never mainstreamed (unless my memory is faulty on this -- it has been several years). The rumor was that Google would put Dart support into Chrome and suddenly web apps like Gmail and Maps and G-Suite would see a 20x performance increase while using fewer resources, all because they had been re-written in Dart, and that would push the rest of the web to at least seriously consider Dart if not adopt it. Clearly that didn't happen.
Yes the GP comment was about their Dart support in Chrome that never went mainstream, then they cancelled it. My comment about TypeScript was an overall view on the ecosystem. Even Angular abandoned Dart.
Yes, basically Dart/Flutter now embraces being a full fledged standalone cross-platform client development tool. Lately, desktop platforms are embraced as well. In order to lure C++/Qt/wxWidgets, C#/WPF, Delphi, etc... devs, native multi-threading support is vital I believe. Otherwise, Flutter will keep the reputation of "a sandboxed tool for cute weather apps development" among such devs.
