Support mixin application equivalence in impact_test.

tests/compiler/dart2js/kernel/impact_test.dart

Index: tests/compiler/dart2js/kernel/impact_test.dart
diff --git a/tests/compiler/dart2js/kernel/impact_test.dart b/tests/compiler/dart2js/kernel/impact_test.dart
index 89bee6244a8bfbb10ac8e467fe05023d6ea975fd..5fd2411e036e09f56319ec7d85920b5eb9c3db90 100644
--- a/tests/compiler/dart2js/kernel/impact_test.dart
+++ b/tests/compiler/dart2js/kernel/impact_test.dart
@@ -184,6 +184,8 @@ main() {
   testNativeMethodCreates();
   testNativeMethodReturns();
   testNativeField(null);
+  testMixinInstantiation();
+  testNamedMixinInstantiation();
 }
 
 testEmpty() {}
@@ -626,6 +628,8 @@ class NativeClass {
   factory NativeClass._() { throw new UnsupportedError("Not supported"); }
 }
 testNativeField(NativeClass c) => c.field;
+testMixinInstantiation() => new Sub();
+testNamedMixinInstantiation() => new NamedMixin();
 ''',
   'sdk/tests/compiler/dart2js_native/helper.dart': '''
 import 'dart:_js_helper';
@@ -644,6 +648,12 @@ class GenericClass<X, Y> {
 typedef Typedef();
 typedef X GenericTypedef<X, Y>(Y y);
 
+class Super {}
+class Mixin1 {}
+class Mixin2 {}
+class Sub extends Super with Mixin1, Mixin2 {}
+class NamedMixin = Super with Mixin1, Mixin2;
+
 const String _serializedScriptValue =
     'num|String|bool|'
     'JSExtendableArray|=Object';