[MatthewPhillips]

I think the best example of this is Windows 8, which has 2 application environments, .NET and Trident (The IE10 rendering engine). They are, for all intents and purposes, on equal footing with each other, and an end user can't tell which environment an application uses.

[flatline3]

In that case, it's no longer standard or portable HTML/JS, no?

[MatthewPhillips]

The engine that powers it is exactly the same, the difference is additional APIs (that add functionality, not performance). Everyone already agrees that HTML/JS needs more APIs.