Create ResolutionEnqueuer after library loading.

pkg/compiler/lib/src/js_backend/backend_helpers.dart

 // Copyright (c) 2015, 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.
 
 library dart2js.js_backend.helpers;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers, Uris;
 import '../common_elements.dart' show CommonElements, ElementEnvironment;
 import '../elements/elements.dart' show PublicName;
@@ skipping 76 matching lines @@
   FunctionEntity findCoreHelper(String name) => _env
       .lookupLibraryMember(commonElements.coreLibrary, name, required: true);
 
   ConstructorEntity _findConstructor(ClassEntity cls, String name) =>
       _env.lookupConstructor(cls, name, required: true);
 
   void onLibrariesLoaded(LoadedLibraries loadedLibraries) {
     assert(loadedLibraries.containsLibrary(Uris.dart_core));
     assert(loadedLibraries.containsLibrary(DART_INTERCEPTORS));
     assert(loadedLibraries.containsLibrary(DART_JS_HELPER));
+  }
 
+  void onResolutionStart() {
     // TODO(johnniwinther): Avoid these. Currently needed to ensure resolution
     // of the classes for various queries in native behavior computation,
     // inference and codegen.
     _env.getThisType(jsArrayClass);
     _env.getThisType(jsExtendableArrayClass);
   }
 
   LibraryEntity _jsHelperLibrary;
   LibraryEntity get jsHelperLibrary =>
       _jsHelperLibrary ??= _env.lookupLibrary(DART_JS_HELPER);
@@ skipping 697 matching lines @@
   /// The class for patch annotations defined in dart:_js_helper.
   ClassEntity get patchAnnotationClass =>
       _patchAnnotationClass ??= _findHelperClass('_Patch');
 
   ClassEntity _nativeAnnotationClass;
 
   /// The class for native annotations defined in dart:_js_helper.
   ClassEntity get nativeAnnotationClass =>
       _nativeAnnotationClass ??= _findHelperClass('Native');
 }