Support parameter metadata.

sdk/lib/_internal/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.
 
 /**
  * This library contains the infrastructure to parse and integrate patch files.
  *
  * Three types of elements can be patched: [LibraryElement], [ClassElement],
  * [FunctionElement]. Patches are introduced in patch libraries which are loaded
  * together with the corresponding origin library. Which libraries that are
@@ skipping 367 matching lines @@
     super.addMember(element);
   }
 }
 
 // TODO(ahe): Get rid of this class.
 class PatchMetadataAnnotation extends MetadataAnnotationX {
   final leg.Constant value = null;
 
   PatchMetadataAnnotation() : super(STATE_DONE);
 
+  tree.Node parseNode(leg.DiagnosticListener listener) => null;
+
   Token get beginToken => null;
   Token get endToken => null;
 }
 
 void patchElement(leg.DiagnosticListener listener,
                    Element origin,
                    Element patch) {
   if (origin == null) {
     listener.reportError(
         patch, leg.MessageKind.PATCH_NON_EXISTING, {'name': patch.name});
@@ skipping 151 matching lines @@
 
 // TODO(johnniwinther): Add unittest when patch is (real) metadata.
 bool isPatchElement(Element element) {
   // TODO(lrn): More checks needed if we introduce metadata for real.
   // In that case, it must have the identifier "native" as metadata.
   for (Link link = element.metadata; !link.isEmpty; link = link.tail) {
     if (link.head is PatchMetadataAnnotation) return true;
   }
   return false;
 }