Introduces the new syntax for deferred loading

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 519 matching lines @@
 
   visitLibraryName(LibraryName node) {
     addToken(node.libraryKeyword);
     node.visitChildren(this);
     add(node.getEndToken().value);
   }
 
   visitImport(Import node) {
     addToken(node.importKeyword);
     visit(node.uri);
+    if (node.isDeferred) {
+      sb.write(' deferred');
+    }
     if (node.prefix != null) {
-      sb.write(' ');
-      addToken(node.asKeyword);
+      sb.write(' as ');
       visit(node.prefix);
     }
     if (node.combinators != null) {
       sb.write(' ');
       visit(node.combinators);
     }
     add(node.getEndToken().value);
   }
 
   visitExport(Export node) {
@@ skipping 62 matching lines @@
   }
 
   visitStatement(Statement node) {
     throw 'internal error'; // Should not be called.
   }
 
   visitStringNode(StringNode node) {
     throw 'internal error'; // Should not be called.
   }
 }