dart2js: Register helpers for updating send to type variable.

pkg/compiler/lib/src/common/backend_api.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.
 
 library dart2js.backend_api;
 
 import 'dart:async' show Future;
 
 import '../compiler.dart' show
     Compiler;
@@ skipping 194 matching lines @@
   /// Call this method to enable support for `noSuchMethod`.
   void enableNoSuchMethod(Enqueuer enqueuer) {}
 
   /// Returns whether or not `noSuchMethod` support has been enabled.
   bool get enabledNoSuchMethod => false;
 
   /// Call this method to enable support for isolates.
   void enableIsolateSupport(Enqueuer enqueuer) {}
 
   void registerRequiredType(DartType type, Element enclosingElement) {}
-  void registerClassUsingVariableExpression(ClassElement cls) {}
 
   void registerConstSymbol(String name, Registry registry) {}
   void registerNewSymbol(Registry registry) {}
 
   bool isNullImplementation(ClassElement cls) {
     return cls == compiler.nullClass;
   }
 
   ClassElement get intImplementation => compiler.intClass;
   ClassElement get doubleImplementation => compiler.doubleClass;
@@ skipping 136 matching lines @@
 
   void forgetElement(Element element) {}
 
   void registerMainHasArguments(Enqueuer enqueuer) {}
 
   void registerAsyncMarker(FunctionElement element,
                            Enqueuer enqueuer,
                            Registry registry) {}
 }