Revert "Add native_testing library to mock @Native classes"

tests/compiler/dart2js_native/native_constructor_name_test.dart

Index: tests/compiler/dart2js_native/native_constructor_name_test.dart
diff --git a/tests/compiler/dart2js_native/native_constructor_name_test.dart b/tests/compiler/dart2js_native/native_constructor_name_test.dart
index 34e6734c61d4da66086997a30a2fee691dc1b492..76a30d79885de87f942cdf1cef320fa5a0f1839e 100644
--- a/tests/compiler/dart2js_native/native_constructor_name_test.dart
+++ b/tests/compiler/dart2js_native/native_constructor_name_test.dart
@@ -8,7 +8,8 @@
 // This could be done by renaming the Dart constructor or by being able to check
 // that objects are Dart classes.
 
-import "native_testing.dart";
+import "dart:_js_helper";
+import "package:expect/expect.dart";
 
 class A {}
 
@@ -22,11 +23,9 @@ makeZ() native ;
 void setup() native """
 function A(){}
 makeZ = function(){return new A};
-self.nativeConstructor(A);
 """;
 
 main() {
-  nativeTesting();
   setup();
 
   var a = new A();