There is a standard for JavaScript, a spec to implement. And new features in the JS language evolve out of a standards process that involves all the browser mak

There is a standard for JavaScript, a spec to implement. And new features in the JS language evolve out of a standards process that involves all the browser makers (as well as others). As a result, you can write a new implementation of it, and people do. There is no standard or spec for NaCl, PNaCl or PPAPI. Those things are still being developed, and they change a lot (talk to people that develop for that API to get an idea of how things can change with each 6-week update of Chrome). To implement those, you need to basically "do what Google's implementation does." Trying to track that large and complex - and changing - implementation is practically impossible.