dart2js: Change how super tear-offs are registered.

pkg/compiler/lib/src/js_backend/codegen/glue.dart

 // Copyright (c) 2014, 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 code_generator_dependencies;
 
 import '../backend_helpers.dart' show
     BackendHelpers;
 import '../js_backend.dart';
 
@@ skipping 268 matching lines @@
 
   // TODO(sra,johnniwinther): Should this be part of CodegenRegistry?
   void registerNativeBehavior(NativeBehavior nativeBehavior, node) {
     if (nativeBehavior == null) return;
     _enqueuer.nativeEnqueuer.registerNativeBehavior(nativeBehavior, node);
   }
 
   ConstantValue getDefaultParameterValue(ParameterElement elem) {
     return _backend.constants.getConstantValueForVariable(elem);
   }
+
+  FunctionElement get closureFromTearOff => _backend.helpers.closureFromTearOff;
 }