No, I wouldn't consider it their duty. OTOH, the last time that Apple promised an open spec protocol (Facetime) I would have expected Google (or someone) to provide a high quality Android implementation. Apple didn't follow through.

I don't personally have a problem with the standards that Google has advocated. Dart is unlikely to succeed, IMO, but I would like to see NativeClient (or something like it) picked up by the other browsers.