Introduces the new syntax for deferred loading

sdk/lib/_internal/compiler/implementation/tree/nodes.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;
 
 abstract class Visitor<R> {
   const Visitor();
 
   R visitNode(Node node);
@@ skipping 1783 matching lines @@
 /**
  * An [:import:] library tag.
  *
  * An import tag is dependency on another library where the exported identifiers
  * are put into the import scope of the importing library. The import scope is
  * only visible inside the library.
  */
 class Import extends LibraryDependency {
   final Identifier prefix;
   final Token importKeyword;
+  final bool isDeferred;
 
   Import(this.importKeyword, StringNode uri,
          this.prefix, NodeList combinators,
-         Link<MetadataAnnotation> metadata)
+         Link<MetadataAnnotation> metadata,
+         {this.isDeferred})
       : super(uri, combinators, metadata);
 
   bool get isImport => true;
 
   Import asImport() => this;
 
-  Token get asKeyword => prefix == null ? null : uri.getEndToken().next;
-
   accept(Visitor visitor) => visitor.visitImport(this);
 
   visitChildren(Visitor visitor) {
     uri.accept(visitor);
     if (prefix != null) prefix.accept(visitor);
     if (combinators != null) combinators.accept(visitor);
   }
 
   Token getBeginToken() => importKeyword;
 
@@ skipping 281 matching lines @@
 }
 
 class IsInterpolationVisitor extends Visitor<bool> {
   const IsInterpolationVisitor();
   bool visitNode(Node node) => false;
   bool visitStringInterpolation(StringInterpolation node) => true;
   bool visitStringJuxtaposition(StringJuxtaposition node)
       => node.isInterpolation;
 }