Add a way to use shared CanonicalName root to deserialize Program.

pkg/kernel/test/type_subtype_test.dart

Index: pkg/kernel/test/type_subtype_test.dart
diff --git a/pkg/kernel/test/type_subtype_test.dart b/pkg/kernel/test/type_subtype_test.dart
index 56b23398f8e032395ed7fb5c52a2fc3b3b5fbeed..b34db7dd6143eb3c441667dddfd17a58794382b7 100644
--- a/pkg/kernel/test/type_subtype_test.dart
+++ b/pkg/kernel/test/type_subtype_test.dart
@@ -136,7 +136,7 @@ MockSubtypeTester makeSubtypeTester(Map<String, List<String>> testcase) {
       }
     }
   }
-  var program = new Program([environment.dummyLibrary]);
+  var program = new Program(libraries: [environment.dummyLibrary]);
   var hierarchy = new ClassHierarchy(program);
   return new MockSubtypeTester(
       hierarchy, objectClass.rawType, functionClass.rawType, environment);