Start allowing mixin application extensions.

sdk/lib/_internal/compiler/implementation/elements/modelx.dart

 // Copyright (c) 2013, 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 elements.modelx;
 
 import 'dart:uri';
 
 import 'elements.dart';
 import '../../compiler.dart' as api;
@@ skipping 1760 matching lines @@
       return 'patch ${super.toString()}';
     } else if (patch != null) {
       return 'origin ${super.toString()}';
     } else {
       return super.toString();
     }
   }
 }
 
 class MixinApplicationElementX extends BaseClassElementX {
-  final MixinApplication cachedNode;
+  final Node cachedNode;
 
   FunctionElement constructor;
   ClassElement mixin;
 
   // TODO(kasperl): The analyzer complains when I don't have these two
   // fields. This is pretty weird. I cannot replace them with getters.
   final ClassElement patch = null;
   final ClassElement origin = null;
 
   MixinApplicationElementX(SourceString name, Element enclosing, int id,
@@ skipping 157 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }