They try to develop most new features as extensions first these days. It keeps the release cycles from impacting each other and lets them make sure that the ex

They try to develop most new features as extensions first these days. It keeps the release cycles from impacting each other and lets them make sure that the extension APIs remain useful for other developers. If it turns out to be a good feature they'll either bundle the extension or build it into the browser from the extension. That's not always something people celebrate though, see the pocket stuff.