I highlighting this feature for this particular crowd because the same bits that make the html web applications work on BlackBerry10 is what drives the new Chrome. This means that the guys making the chrome _really_ do care that html applications work well.

As for overhead the browser team has always concerned itself with keeping its footprint down both in memory and cpu and by using JS+HTML our total overhead was actually reduced compared to running another framework along side WebKit just for the Chrome. Checkout the above second video for more in depth presentation on this.

Disclaimer: I am part of the WebKit team at RIM these opinions are my own