Support parameter metadata.

sdk/lib/_internal/compiler/implementation/tree/unparser.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.
 
 part of tree;
 
 String unparse(Node node) {
   Unparser unparser = new Unparser();
   unparser.unparse(node);
   return unparser.result;
@@ skipping 341 matching lines @@
 
   visitTypeVariable(TypeVariable node) {
     visit(node.name);
     if (node.bound != null) {
       sb.write(' extends ');
       visit(node.bound);
     }
   }
 
   visitVariableDefinitions(VariableDefinitions node) {
+    if (node.metadata != null) {
+      visit(node.metadata);
+      sb.write(' ');
+    }
     visit(node.modifiers);
     if (!node.modifiers.nodes.isEmpty) {
       sb.write(' ');
     }
     if (node.type != null) {
       visit(node.type);
       sb.write(' ');
     }
     visit(node.definitions);
   }
@@ skipping 194 matching lines @@
     addToken(node.ofKeyword);
     visit(node.name);
     add(node.getEndToken().value);
   }
 
   visitCombinator(Combinator node) {
     addToken(node.keywordToken);
     visit(node.identifiers);
   }
 
+  visitMetadata(Metadata node) {
+    addToken(node.token);
+    visit(node.expression);
+  }
+
   visitNode(Node node) {
     throw 'internal error'; // Should not be called.
   }
 
   visitExpression(Expression node) {
     throw 'internal error'; // Should not be called.
   }
 
   visitLibraryTag(LibraryTag node) {
     throw 'internal error'; // Should not be called.
@@ skipping 20 matching lines @@
   }
 
   visitStatement(Statement node) {
     throw 'internal error'; // Should not be called.
   }
 
   visitStringNode(StringNode node) {
     throw 'internal error'; // Should not be called.
   }
 }