dart2js: Not all interceptor accesses are safe.

pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart

Index: pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart b/pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart
index 98691d20edd98b90c6aa0cf5e4a3cd14f7a17bf7..a543208cb2a1265976f8a1e35b15227dbc561618 100644
--- a/pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/new_emitter/emitter.dart
@@ -128,9 +128,10 @@ class Emitter implements emitterTask.Emitter {
   }
 
   @override
-  js.PropertyAccess interceptorClassAccess(ClassElement element) {
-    // Interceptors are eagerly constructed. It's safe to just access them.
-    return _globalPropertyAccess(element);
+  js.Expression interceptorClassAccess(ClassElement element) {
+    // Some interceptors are eagerly constructed. However, native interceptors
+    // aren't.
+    return js.js('#.ensureResolved()', _globalPropertyAccess(element));
   }
 
   @override