Isolates: allow sending of arbitrary objects in dart2js.

sdk/lib/_internal/compiler/js_lib/native_helper.dart

Index: sdk/lib/_internal/compiler/js_lib/native_helper.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/native_helper.dart b/sdk/lib/_internal/compiler/js_lib/native_helper.dart
index 7de3c6fb634a4f0fa29faa7f89138f08ca17cbb9..798bf02f61dc93e9580ff9f29fa294718ea72fb3 100644
--- a/sdk/lib/_internal/compiler/js_lib/native_helper.dart
+++ b/sdk/lib/_internal/compiler/js_lib/native_helper.dart
@@ -443,7 +443,8 @@ applyHooksTransformer(transformer, hooks) {
 const _baseHooks = const JS_CONST(r'''
 function() {
   function typeNameInChrome(o) {
-    var name = o.constructor.name;
+    var constructor = o.constructor;
+    if (constructor) var name = constructor.name;
     if (name) return name;
     var s = Object.prototype.toString.call(o);
     return s.substring(8, s.length - 1);