Handle forwarding constructors to unnamed mixin applications

tests/compiler/dart2js/equivalence/check_functions.dart

 // Copyright (c) 2017, 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.
 
 /// Equivalence test functions for data objects.
 
 library dart2js.equivalence.functions;
 
 import 'package:expect/expect.dart';
 import 'package:compiler/src/common/resolution.dart';
@@ skipping 1005 matching lines @@
         fragment2.invokeMain, areJsNodesEquivalent, js.nodeToString);
   } else if (fragment1 is DeferredFragment && fragment2 is DeferredFragment) {
     check(fragment1, fragment2, 'name', fragment1.name, fragment2.name);
   }
 }
 
 void checkEmitterLibraries(
     Library library1, Library library2, TestStrategy strategy) {
   check(library1, library2, 'uri', library1.uri, library2.uri);
   checkLists(library1.classes, library2.classes, 'classes',
-      (a, b) => a.element.name == b.element.name,
+      (a, b) => a.name.key == b.name.key,
       onSameElement: (a, b) => checkEmitterClasses(a, b, strategy));
   checkLists(library1.statics, library2.statics, 'statics',
       (a, b) => a.name.key == b.name.key,
       onSameElement: (a, b) => checkEmitterMethods(a, b, strategy));
   checkLists(
       library1.staticFieldsForReflection,
       library2.staticFieldsForReflection,
       'staticFieldsForReflection on $library1/$library2',
       (a, b) => a.name.key == b.name.key,
       onSameElement: checkEmitterFields);
@@ skipping 183 matching lines @@
         print('  ${js.nodeToString(node1)}');
         print('  ${js.nodeToString(node2)}');
       }
       return expectedValue == label2;
     } else {
       labelsMap[label1] = label2;
       return true;
     }
   }
 }