fix #30030, fix #27327 - fix tearoffs and various Object member bugs

pkg/dev_compiler/tool/input_sdk/private/js_array.dart

Index: pkg/dev_compiler/tool/input_sdk/private/js_array.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/js_array.dart b/pkg/dev_compiler/tool/input_sdk/private/js_array.dart
index 260f58d79819ec38525a6180cb72b3fb9d81586c..4736850f36869b57f143be04e4d07cdde40029cb 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/js_array.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/js_array.dart
@@ -580,6 +580,8 @@ class JSArray<E> implements List<E>, JSIndexable<E> {
   Map<int, E> asMap() {
     return new ListMapView<E>(this);
   }
+
+  Type get runtimeType => wrapType(JS('', '#(#)', getGenericClass(List), E));
 }
 
 /**