Revert of cc: Remove use of PassAs() and constructor-casting with scoped_ptr.

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 3c6c4403690d8bd11b0484b05bc5168bdb5af1a0..b35e437bd3a955467c2ffe1ca9df32403470c54c 100644
--- a/cc/trees/occlusion_tracker_unittest.cc
+++ b/cc/trees/occlusion_tracker_unittest.cc
@@ -121,8 +121,13 @@
     return make_scoped_refptr(new ContentLayerType());
   }
 
-  template <typename T>
-  static LayerPtrType PassLayerPtr(T* layer) {
+  static LayerPtrType PassLayerPtr(ContentLayerPtrType* layer) {
+    LayerPtrType ref(*layer);
+    *layer = NULL;
+    return ref;
+  }
+
+  static LayerPtrType PassLayerPtr(LayerPtrType* layer) {
     LayerPtrType ref(*layer);
     *layer = NULL;
     return ref;
@@ -151,9 +156,12 @@
   }
   static int next_layer_impl_id;
 
-  template <typename T>
-  static LayerPtrType PassLayerPtr(T* layer) {
+  static LayerPtrType PassLayerPtr(LayerPtrType* layer) {
     return layer->Pass();
+  }
+
+  static LayerPtrType PassLayerPtr(ContentLayerPtrType* layer) {
+    return layer->PassAs<LayerType>();
   }
 
   static void DestroyLayer(LayerPtrType* layer) { layer->reset(); }
@@ -278,7 +286,7 @@
 
   void DestroyLayers() {
     Types::DestroyLayer(&root_);
-    render_surface_layer_list_ = nullptr;
+    render_surface_layer_list_.reset();
     render_surface_layer_list_impl_.clear();
     replica_layers_.clear();
     mask_layers_.clear();