Support parsing of enums in dart2js.

sdk/lib/_internal/compiler/implementation/tree/prettyprint.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;
 
 /**
  * Pretty-prints Node tree in XML-like format.
  *
  * TODO(smok): Add main() to run from command-line to print out tree for given
@@ skipping 154 matching lines @@
   }
 
   visitDoWhile(DoWhile node) {
     visitNodeWithChildren(node, "DoWhile");
   }
 
   visitEmptyStatement(EmptyStatement node) {
     visitNodeWithChildren(node, "EmptyStatement");
   }
 
+  visitEnum(Enum node) {
+    visitNodeWithChildren(node, "Enum");
+  }
+
   visitExpressionStatement(ExpressionStatement node) {
     visitNodeWithChildren(node, "ExpressionStatement");
   }
 
   visitFor(For node) {
     visitNodeWithChildren(node, "For");
   }
 
   visitForIn(ForIn node) {
     visitNodeWithChildren(node, "ForIn");
@@ skipping 321 matching lines @@
   }
 
   visitGotoStatement(GotoStatement node) {
     unimplemented('visitNode', node: node);
   }
 
   unimplemented(String message, {Node node}) {
     throw message;
   }
 }