material content implementation

[dskinner]

Material content can act independently of the material itself, being clipped by the material's bounds. There's a lot of interesting cases for interactions with this such as resolving content layout that is masked and clipped by a floating action button that on click removes mask and animates to the encompass content's bounds.

The question then becomes, what is content .. but the layout of text and images, both of which are supported to some degree by the Material type today. So, how should this be laid out and how should the various types interact? Is a distinction of material vs content required at the type level or is this an api issue? I'm leaning towards the latter.