Require jsInteropObject type to be resolved before we use it in native behaviors

This fixes a failing interop test in the bots.

R=sra@google.com

Review URL: https://codereview.chromium.org/1484273002 .

pkg/compiler/lib/src/native/behavior.dart

@@ -818,8 +818,9 @@ class NativeBehavior {
           // annotations. This means that to some degree we still use the return
           // type to decide whether to include native types, even if we don't
           // trust the type annotation.
-          typesInstantiated.add(
-              backend.helpers.jsJavaScriptObjectClass.thisType);
+          ClassElement cls = backend.helpers.jsJavaScriptObjectClass;
+          cls.ensureResolved(resolution);
+          typesInstantiated.add(cls.thisType);
         } else {
           // Otherwise, when the declared type is a Dart type, we do not
           // register an allocation because we assume it cannot be instantiated

tests/html/js_dart_to_string_test.dart

@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 @JS()
-library js_typed_interop_test;
+library js_dart_to_string_test;
 
 import 'dart:html';