fix list_test for strong mode, and fix DDC List constructors

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart

Index: pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart b/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart
index 4075646b8e11fc05a496381658b5d14c63ab11f9..b33748a49c1a00c0592b97d31fd695b6d994c538 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart
@@ -7,6 +7,11 @@ part of dart._runtime;
 /// by the Dart runtime.
 // TODO(ochafik): Rewrite some of these in Dart when possible.
 
+/// The JavaScript undefined constant.
+/// 
+/// This is initialized by DDC to JS void 0.
+const undefined = null;
+
 defineProperty(obj, name, desc) =>
     JS('', 'Object.defineProperty(#, #, #)', obj, name, desc);