Find native classes with mixins in NativeClassFinder

pkg/compiler/lib/src/native/resolver.dart

 // Copyright (c) 2014, 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.
 
 import 'package:front_end/src/fasta/scanner.dart'
     show BeginGroupToken, StringToken, Token;
 import 'package:front_end/src/fasta/scanner.dart' as Tokens show EOF_TOKEN;
 
 import '../common.dart';
 import '../common_elements.dart' show CommonElements, ElementEnvironment;
@@ skipping 388 matching lines @@
         }
       } else {
         _tagOwner[tag] = cls;
       }
     }
   }
 
   /// Returns the name of the super class of [cls] or `null` of [cls] has
   /// no explicit superclass.
   String _findExtendsNameOfClass(ClassEntity cls) {
-    return _elementEnvironment.getSuperClass(cls)?.name;
+    return _elementEnvironment
+        .getSuperClass(cls, skipUnnamedMixinApplications: true)
+        ?.name;
   }
 
   /// Adds all subclasses of [nativeClasses] found in [libraries] to
   /// [nativeClasses].
   void _processSubclassesOfNativeClasses(
       Iterable<LibraryEntity> libraries, Set<ClassEntity> nativeClasses) {
     Set<ClassEntity> nativeClassesAndSubclasses = new Set<ClassEntity>();
     // Collect potential subclasses, e.g.
     //
     //     class B extends foo.A {}
@@ skipping 144 matching lines @@
 
   Iterable<ConstantValue> fields = constructedObject.fields.values;
   // TODO(sra): Better validation of the constant.
   if (fields.length != 1 || fields.single is! StringConstantValue) {
     throw new SpannableAssertionFailure(
         spannable, 'Annotations needs one string: ${value.toStructuredText()}');
   }
   StringConstantValue specStringConstant = fields.single;
   return specStringConstant.toDartString().slowToString();
 }