What he's saying is that Mozilla is taking Chrome's API as the base and then adding more interfaces to it, to make it more powerful than Chrome's API and hopefu

What he's saying is that Mozilla is taking Chrome's API as the base and then adding more interfaces to it, to make it more powerful than Chrome's API and hopefully as close to Firefox's current add-on-capabilities as possible. For example Mozilla has already added an API, so that NoScript can now be ported to WebExtensions.