Support shadows on the root RenderNode

bug:13211941

Cleans up some of the RenderNode method naming

Also removes unnecessary clip/save/restores, clipping shadows
predictably, as drawn by the parent, before drawing (and clipping,
etc.) the shadow casting child.

Change-Id: I795115e1fb869bbbdd7be43e279b97490fecc7e0
5 files changed