Add native_testing library to mock @Native classes

tests/compiler/dart2js_native/issue9182_test.dart

Index: tests/compiler/dart2js_native/issue9182_test.dart
diff --git a/tests/compiler/dart2js_native/issue9182_test.dart b/tests/compiler/dart2js_native/issue9182_test.dart
index 5e06b3585abe89cef9631d455a381991f50f755c..1b5d1acc837902c129b358897910a1f6dff31241 100644
--- a/tests/compiler/dart2js_native/issue9182_test.dart
+++ b/tests/compiler/dart2js_native/issue9182_test.dart
@@ -5,8 +5,7 @@
 // Regression test for Issue 9182.  The generative constructor body function
 // should not have the interceptor calling convention.
 
-import "dart:_js_helper";
-import "package:expect/expect.dart";
+import "native_testing.dart";
 
 @Native("A")
 class Foo {
@@ -28,16 +27,17 @@ class Bar {
 void setup() native r"""
 function A(){}
 makeA = function() { return new A; };
+self.nativeConstructor(A);
 """;
 
 makeA() native ;
 
 main() {
+  nativeTesting();
   setup();
 
-  var things = [new Foo(), new Bar(30, 40)];
-  var foo = things[0];
-  var bar = things[1];
+  var foo = confuse(new Foo());
+  var bar = confuse(new Bar(30, 40));
 
   Expect.equals(123, foo.Bar()); // Ensure that Foo.Bar is used.