Add native_testing library to mock @Native classes

tests/compiler/dart2js_native/native_field_invocation3_test.dart

Index: tests/compiler/dart2js_native/native_field_invocation3_test.dart
diff --git a/tests/compiler/dart2js_native/native_field_invocation3_test.dart b/tests/compiler/dart2js_native/native_field_invocation3_test.dart
index 0944f175a329875108f1980f484527b5b791a68d..18390cd2be551542cb0fbc2830cded6dd74fbb2a 100644
--- a/tests/compiler/dart2js_native/native_field_invocation3_test.dart
+++ b/tests/compiler/dart2js_native/native_field_invocation3_test.dart
@@ -2,14 +2,14 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import "dart:_js_helper";
-import "package:expect/expect.dart";
+import "native_testing.dart";
 
 makeCC() native ;
 
 void setup() native """
 function CC() {}
 makeCC = function() { return new CC; }
+self.nativeConstructor(CC);
 """;
 
 @Native("CC")
@@ -32,6 +32,7 @@ wrap(cb) {
 }
 
 main() {
+  nativeTesting();
   setup();
   var c = makeCC();
   c.init();