cc: Clean up iterator template to only take 1 parameter.

cc/trees/occlusion_tracker_unittest.cc

Index: cc/trees/occlusion_tracker_unittest.cc
diff --git a/cc/trees/occlusion_tracker_unittest.cc b/cc/trees/occlusion_tracker_unittest.cc
index 1704a23aaf504239419f80e9cad1bef22e5a5ab3..3a4cd045c1e2d776cc19275aa582cdb6e49fe9fc 100644
--- a/cc/trees/occlusion_tracker_unittest.cc
+++ b/cc/trees/occlusion_tracker_unittest.cc
@@ -122,10 +122,7 @@ struct OcclusionTrackerTestMainThreadTypes {
   typedef TestContentLayer ContentLayerType;
   typedef scoped_refptr<Layer> LayerPtrType;
   typedef scoped_refptr<ContentLayerType> ContentLayerPtrType;
-  typedef LayerIterator<Layer,
-                        RenderSurfaceLayerList,
-                        RenderSurface,
-                        LayerIteratorActions::FrontToBack> TestLayerIterator;
+  typedef LayerIterator<Layer> TestLayerIterator;
   typedef OcclusionTracker OcclusionTrackerType;
 
   static LayerPtrType CreateLayer(HostType*  host) { return Layer::Create(); }
@@ -155,10 +152,7 @@ struct OcclusionTrackerTestImplThreadTypes {
   typedef TestContentLayerImpl ContentLayerType;
   typedef scoped_ptr<LayerImpl> LayerPtrType;
   typedef scoped_ptr<ContentLayerType> ContentLayerPtrType;
-  typedef LayerIterator<LayerImpl,
-                        LayerImplList,
-                        RenderSurfaceImpl,
-                        LayerIteratorActions::FrontToBack> TestLayerIterator;
+  typedef LayerIterator<LayerImpl> TestLayerIterator;
   typedef OcclusionTrackerImpl OcclusionTrackerType;
 
   static LayerPtrType CreateLayer(HostType* host) {