Merge CommonElements and BackendHelpers!

pkg/compiler/lib/src/closure.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 closureToClassMapper;
 
 import 'common/names.dart' show Identifiers;
 import 'common/resolution.dart' show ParsingContext, Resolution;
 import 'common/tasks.dart' show CompilerTask;
 import 'common.dart';
@@ skipping 205 matching lines @@
       this.node, String name, Compiler compiler, LocalFunctionElement closure)
       : this.methodElement = closure,
         super(
             name,
             closure.compilationUnit,
             // By assigning a fresh class-id we make sure that the hashcode
             // is unique, but also emit closure classes after all other
             // classes (since the emitter sorts classes by their id).
             compiler.idGenerator.getNextFreeId(),
             STATE_DONE) {
-    JavaScriptBackend backend = compiler.backend;
     ClassElement superclass = methodElement.isInstanceMember
-        ? backend.helpers.boundClosureClass
-        : backend.helpers.closureClass;
+        ? compiler.commonElements.boundClosureClass
+        : compiler.commonElements.closureClass;
     superclass.ensureResolved(compiler.resolution);
     supertype = superclass.thisType;
     interfaces = const Link<ResolutionDartType>();
     thisType = rawType = new ResolutionInterfaceType(this);
     allSupertypesAndSelf =
         superclass.allSupertypesAndSelf.extendClass(thisType);
     callType = methodElement.type;
   }
 
   Iterable<ClosureFieldElement> get closureFields => _closureFields;
@@ skipping 985 matching lines @@
 ///
 /// Move the below classes to a JS model eventually.
 ///
 abstract class JSEntity implements Entity {
   Entity get declaredEntity;
 }
 
 abstract class PrivatelyNamedJSEntity implements JSEntity {
   Entity get rootOfScope;
 }