Added support for exports and re-exports.

lib/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.
 
 /**
  * Pretty-prints Node tree in XML-like format.
  *
  * TODO(smok): Add main() to run from command-line to print out tree for given
  * .dart file.
  */
@@ skipping 402 matching lines @@
   }
 
   visitGotoStatement(GotoStatement node) {
     unimplemented('visitNode', node: node);
   }
 
   visitImport(Import node) {
     unimplemented('visitNode', node: node);
   }
 
+  visitLibraryDependency(Node node) {
+    unimplemented('visitNode', node: node);
+  }
+
   visitLibraryName(LibraryName node) {
     unimplemented('visitNode', node: node);
   }
 
   visitLibraryTag(LibraryTag node) {
     unimplemented('visitNode', node: node);
   }
 
   visitLiteral(Literal node) {
     unimplemented('visitNode', node: node);
@@ skipping 24 matching lines @@
   }
 
   visitStringNode(StringNode node) {
     unimplemented('visitNode', node: node);
   }
 
   unimplemented(String message, {Node node}) {
     throw message;
   }
 }