bug:27873093 Adds the simple overdraw avoidance optimization to the new pipeline. This means when LayerBuilder defers draws that are opaque over the full area of the repaint region, it will discard all drawing content beneth. Also moves a lot of complexity out of BakedOpState's header. Change-Id: Iffca6d8e1b170ef31a5d6c83d25592670e02323d