> I was just pointing additional confusion if mixins extend Widget, given that their naming pattern doesn't convey the mixin semantic anymore. 

But the naming pattern doesn't change depending on whether or not you extend Widget.   Either way it's called Scrollable.  Note the next line item in the google doc:

> Mixins SHOULD *not* be postfixed by Mixin (ala dgrid or dtreemap, so Selection not SelectionMixin for example)