Implement super in mixins.

pkg/compiler/lib/src/parser/partial_elements.dart

 // Copyright (c) 2015, 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.parser.partial_elements;
 
 import '../common.dart';
 import '../common/resolution.dart' show Parsing, Resolution;
 import '../dart_types.dart' show DynamicType;
 import '../elements/elements.dart'
@@ skipping 254 matching lines @@
     if (node.type != null) {
       type = resolution.reporter.withCurrentElement(element, () {
         return resolution.resolveTypeAnnotation(element, node.type);
       });
     } else {
       type = const DynamicType();
     }
     assert(type != null);
     return type;
   }
+
+  PartialFieldList copy() {
+    return new PartialFieldList(beginToken, endToken, modifiers, hasParseError);
+  }
 }
 
 class PartialTypedefElement extends TypedefElementX with PartialElement {
   PartialTypedefElement(
       String name, Element enclosing, Token beginToken, Token endToken)
       : super(name, enclosing) {
     this.beginToken = beginToken;
     this.endToken = endToken;
   }
 
@@ skipping 168 matching lines @@
       } on ParserError catch (e) {
         partial.hasParseError = true;
         return new ErrorNode(element.position, e.reason);
       }
       Node node = listener.popNode();
       assert(listener.nodes.isEmpty);
       return node;
     });
   });
 }