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

cc/trees/layer_tree_host_unittest_no_message_loop.cc

Index: cc/trees/layer_tree_host_unittest_no_message_loop.cc
diff --git a/cc/trees/layer_tree_host_unittest_no_message_loop.cc b/cc/trees/layer_tree_host_unittest_no_message_loop.cc
index 9e38f1c8c5ff052aaee24d41f68f74b1872a94f8..862f34bb60af57f7a33cae1eb63b1853d35b3ce4 100644
--- a/cc/trees/layer_tree_host_unittest_no_message_loop.cc
+++ b/cc/trees/layer_tree_host_unittest_no_message_loop.cc
@@ -113,8 +113,8 @@
 
   void TearDownLayerTreeHost() {
     // Explicit teardown to make failures easier to debug.
-    layer_tree_host_ = nullptr;
-    root_layer_ = nullptr;
+    layer_tree_host_.reset();
+    root_layer_ = NULL;
   }
 
   // All protected member variables are accessed only on |no_loop_thread_|.