Revert of cc: Add occlusion checker as a fixed view of occlusion tracker.

cc/trees/occlusion_tracker.cc

Index: cc/trees/occlusion_tracker.cc
diff --git a/cc/trees/occlusion_tracker.cc b/cc/trees/occlusion_tracker.cc
index 8fdd6e256fad0b0d5543883c544b8878446cf408..f233e074a9ba8b0a1441658ad2751ec3dbd907af 100644
--- a/cc/trees/occlusion_tracker.cc
+++ b/cc/trees/occlusion_tracker.cc
@@ -26,16 +26,6 @@
 
 template <typename LayerType>
 OcclusionTracker<LayerType>::~OcclusionTracker() {}
-
-template <typename LayerType>
-Occlusion OcclusionTracker<LayerType>::GetCurrentOcclusionForLayer(
-    const gfx::Transform& draw_transform) const {
-  DCHECK(!stack_.empty());
-  const StackObject& back = stack_.back();
-  return Occlusion(draw_transform,
-                   back.occlusion_from_outside_target,
-                   back.occlusion_from_inside_target);
-}
 
 template <typename LayerType>
 void OcclusionTracker<LayerType>::EnterLayer(