Handle private dynamic access in impact_test.

tests/compiler/dart2js/kernel/impact_test.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 library dart2js.kernel.impact_test;
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common.dart';
 import 'package:compiler/src/common/names.dart';
@@ skipping 156 matching lines @@
   testSuperGet();
   testSuperFieldSet();
   testSuperSetterSet();
   testSuperClosurization();
   testForwardingConstructor();
   testForwardingConstructorTyped();
   testForwardingConstructorGeneric();
   testEnum();
   testStaticGenericMethod();
   testInstanceGenericMethod();
+  testDynamicPrivateMethodInvoke();
 }
 
 testEmpty() {}
 testNull() => null;
 testTrue() => true;
 testFalse() => false;
 testInt() => 42;
 testDouble() => 37.5;
 testString() => 'foo';
 testStringInterpolation() => '${0}';
@@ skipping 404 matching lines @@
 testEnum() => Enum.A;
 
 List<T> staticGenericMethod<T>(T arg) => [arg];
 testStaticGenericMethod() {
   staticGenericMethod<int>(0);
 }
 
 testInstanceGenericMethod() {
   new GenericClass<int, String>.generative().genericMethod<bool>(false);
 }
+
+testDynamicPrivateMethodInvoke([o]) => o._privateMethod();
 ''',
   'helper.dart': '''
 class Class {
   const Class.generative();
   factory Class.fact() => null;
   const factory Class.redirect() = Class.generative;
 }
 class GenericClass<X, Y> {
   const GenericClass.generative();
   factory GenericClass.fact() => null;
@@ skipping 247 matching lines @@
         visitList(type.optionalParameterTypes),
         type.namedParameters,
         visitList(type.namedParameterTypes));
   }
 }
 
 /// Perform unaliasing of all typedefs nested within a [ResolutionDartType].
 ResolutionDartType unalias(ResolutionDartType type) {
   return const Unaliaser().visit(type);
 }