Add LibraryElementForLink.isDartAsync.

pkg/analyzer/lib/src/summary/link.dart

 // Copyright (c) 2016, 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.
 
 /**
  * This library is capable of producing linked summaries from unlinked
  * ones (or prelinked ones).  It functions by building a miniature
  * element model to represent the contents of the summaries, and then
  * scanning the element model to gather linked information and adding
  * it to the summary data structures.
@@ skipping 2687 matching lines @@
   List<LibraryElementForLink> get exportedLibraries => _exportedLibraries ??=
       _linkedLibrary.exportDependencies.map(_getDependency).toList();
 
   @override
   String get identifier => _absoluteUri.toString();
 
   @override
   List<LibraryElementForLink> get importedLibraries => _importedLibraries ??=
       _linkedLibrary.importDependencies.map(_getDependency).toList();
 
+  @override
+  bool get isDartAsync => _absoluteUri == 'dart:async';
+
   /**
    * If this library is part of the build unit being linked, return the library
    * cycle it is part of.  Otherwise return `null`.
    */
   LibraryCycleForLink get libraryCycleForLink;
 
   @override
   List<UnitElement> get units {
     if (_units == null) {
       UnlinkedUnit definingUnit = definingUnlinkedUnit;
@@ skipping 1355 matching lines @@
           List<int> implicitFunctionTypeIndices) =>
       DynamicTypeImpl.instance;
 
   ReferenceableElementForLink getContainedName(String name) {
     return new NonstaticMemberElementForLink(_constNode);
   }
 
   @override
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }