dart2js: add special getter to Closure class in new emitter.

pkg/compiler/lib/src/js_emitter/program_builder.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 dart2js.js_emitter.program_builder;
 
 import 'js_emitter.dart' show computeMixinClass;
 import 'model.dart';
 
 import '../common.dart';
@@ skipping 335 matching lines @@
     if (element == _compiler.objectClass) {
       Map<String, Selector> selectors =
           classStubGenerator.computeSelectorsForNsmHandlers();
       selectors.forEach((String name, Selector selector) {
         noSuchMethodStubs
             .add(classStubGenerator.generateStubForNoSuchMethod(name,
                                                                 selector));
       });
     }
 
+    if (element == backend.closureClass) {
+      // We add a special getter here to allow for tearing off a closure from
+      // itself.
+      String name = namer.getterNameFromAccessorName(
+          namer.getMappedInstanceName(Compiler.CALL_OPERATOR_NAME));
+      js.Fun function = js.js('function() { return this; }');
+      callStubs.add(_buildStubMethod(name, function));
+    }
+
     ClassElement implementation = element.implementation;
 
     // MixinApplications run through the members of their mixin. Here, we are
     // only interested in direct members.
     if (!onlyForRti && !element.isMixinApplication) {
       implementation.forEachMember(visitMember, includeBackendMembers: true);
     }
 
     List<Field> instanceFields =
         onlyForRti ? const <Field>[] : _buildFields(element, false);
@@ skipping 292 matching lines @@
       _registry.registerConstant(outputUnit, constantValue);
       assert(!_constants.containsKey(constantValue));
       String name = namer.constantName(constantValue);
       String constantObject = namer.globalObjectForConstant(constantValue);
       Holder holder = _registry.registerHolder(constantObject);
       Constant constant = new Constant(name, holder, constantValue);
       _constants[constantValue] = constant;
     }
   }
 }