Fix type in patch_parser.dart.

lib/compiler/implementation/patch_parser.dart

 // Copyright (c) 2012, 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("patchparser");
 #import("dart:uri");
 
 #import("tree/tree.dart", prefix: "tree");
 #import("leg.dart", prefix: 'leg');  // CompilerTask, Compiler.
 #import("apiimpl.dart");
@@ skipping 193 matching lines @@
       if (isMemberPatch) {
         if (element is! FunctionElement) {
           listener.internalErrorOnElement(element,
                                           "Member patch is not a function.");
         }
         if (existing.kind === ElementKind.ABSTRACT_FIELD) {
           if (!element.isAccessor()) {
             listener.internalErrorOnElement(
                 element, "Patching non-accessor with accessor");
           }
-          AbstractField field = existing;
+          AbstractFieldElement field = existing;
           if (element.isGetter()) {
             existing = field.getter;
           } else {
             existing = field.setter;
           }
         }
         if (existing is! FunctionElement) {
           listener.internalErrorOnElement(element,
                                           "No corresponding method for patch.");
         }
@@ skipping 49 matching lines @@
     }
   }
 
   void addMember(Element element) {
     if (isMemberPatch || (isClassPatch && element is ClassElement)) {
       element.addMetadata(popNode());
     }
     super.addMember(element);
   }
 }