Controling style of elements in Injection Points

Hello, I have been experimenting with Web Components and I have an issue,
which I think I have represented fairly clear here:

(Tested on Chrome)
http://codepen.io/dbugger/pen/Hyihd

If I understood correctly, one of the points of web components is to
control the presentation of our component. That is why we have the Shadow
Boundary. BUT what happens with the elements that are represented with
<content>? They are not considered part of the shadow, therefore the styles
that the author decides to apply on them, will "invade" the Web Component.

Any thought on this?

-- 
Enrique Moreno Tent, Web developer
http://enriquemorenotent.com