Convert //cc from scoped_ptr to std::unique_ptr.

cc/test/layer_tree_json_parser.cc

Index: cc/test/layer_tree_json_parser.cc
diff --git a/cc/test/layer_tree_json_parser.cc b/cc/test/layer_tree_json_parser.cc
index 815700bcd06918d4cbd705663a7ea63230a4d3a7..48c757999134d28768e41907a2fb2cccb8341957 100644
--- a/cc/test/layer_tree_json_parser.cc
+++ b/cc/test/layer_tree_json_parser.cc
@@ -166,7 +166,7 @@ scoped_refptr<Layer> ParseTreeFromValue(base::Value* val,
 
 scoped_refptr<Layer> ParseTreeFromJson(std::string json,
                                        ContentLayerClient* content_client) {
-  scoped_ptr<base::Value> val = base::test::ParseJson(json);
+  std::unique_ptr<base::Value> val = base::test::ParseJson(json);
   return ParseTreeFromValue(val.get(), content_client);
 }