Remove unnecessary Rect, better reuse of NinePatch objects

Cloning drawables (which happens a lot) was creating copies of NinePatch
objects, which would cause the hardware renderer to generate more meshes
than necessary. Also avoid keeping a String we don't need (it was interned
but still.) Last but not least, remove 1 RectF per NinePatch in the system.

Change-Id: If4dbfa0c30892c9b00d68875e334fd5c2bde8b94