Remove _WorkerStub hack to make benefit closing an isolate.

dart/sdk/lib/_internal/compiler/implementation/compiler.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 dart2js;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 707 matching lines @@
         const SourceString(""), listClass.getLibrary());
     return _unnamedListConstructor =
         listClass.lookupConstructor(callConstructor);
   }
 
   void scanBuiltinLibraries() {
     jsHelperLibrary = scanBuiltinLibrary('_js_helper');
     interceptorsLibrary = scanBuiltinLibrary('_interceptors');
     foreignLibrary = scanBuiltinLibrary('_foreign_helper');
     isolateHelperLibrary = scanBuiltinLibrary('_isolate_helper');
-    // The helper library does not use the native language extension,
-    // so we manually set the native classes this library defines.
-    // TODO(ngeoffray): Enable annotations on these classes.
-    ClassElement cls =
-        isolateHelperLibrary.find(const SourceString('_WorkerStub'));
-    cls.setNative('"Worker"');
 
     assertMethod = jsHelperLibrary.find(const SourceString('assertHelper'));
     identicalFunction = coreLibrary.find(const SourceString('identical'));
 
     initializeSpecialClasses();
 
     functionClass.ensureResolved(this);
     functionApplyMethod =
         functionClass.lookupLocalMember(const SourceString('apply'));
     jsInvocationMirrorClass.ensureResolved(this);
@@ skipping 587 matching lines @@
 
   void close() {}
 
   toString() => name;
 
   /// Convenience method for getting an [api.CompilerOutputProvider].
   static NullSink outputProvider(String name, String extension) {
     return new NullSink('$name.$extension');
   }
 }