Merge CommonElements and BackendHelpers!

pkg/compiler/lib/src/js_emitter/main_call_stub_generator.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.main_call_stub_generator;
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
 
 import '../elements/entities.dart';
 import '../js/js.dart' as jsAst;
 import '../js/js.dart' show js;
-import '../js_backend/backend_helpers.dart' show BackendHelpers;
 import '../js_backend/js_backend.dart' show JavaScriptBackend;
 
 import 'code_emitter_task.dart' show CodeEmitterTask;
 
 class MainCallStubGenerator {
   final JavaScriptBackend backend;
   final CodeEmitterTask emitterTask;
 
   MainCallStubGenerator(this.backend, this.emitterTask);
 
-  BackendHelpers get helpers => backend.helpers;
-
   /// Returns the code equivalent to:
   ///   `function(args) { $.startRootIsolate(X.main$closure(), args); }`
   jsAst.Expression _buildIsolateSetupClosure(
       FunctionEntity appMain, FunctionEntity isolateMain) {
     jsAst.Expression mainAccess =
         emitterTask.isolateStaticClosureAccess(appMain);
     // Since we pass the closurized version of the main method to
     // the isolate method, we must make sure that it exists.
     return js('function(a){ #(#, a); }',
         [emitterTask.staticFunctionAccess(isolateMain), mainAccess]);
   }
 
   jsAst.Statement generateInvokeMain(FunctionEntity main) {
     jsAst.Expression mainCallClosure = null;
     if (backend.backendUsage.isIsolateInUse) {
-      FunctionEntity isolateMain = helpers.startRootIsolate;
+      FunctionEntity isolateMain = backend.commonElements.startRootIsolate;
       mainCallClosure = _buildIsolateSetupClosure(main, isolateMain);
     } else {
       mainCallClosure = emitterTask.staticFunctionAccess(main);
     }
 
     jsAst.Expression currentScriptAccess =
         emitterTask.generateEmbeddedGlobalAccess(embeddedNames.CURRENT_SCRIPT);
 
     // This code finds the currently executing script by listening to the
     // onload event of all script tags and getting the first script which
@@ skipping 31 matching lines @@
         } else {
           #mainCallClosure([]);
         }
       })''',
         {
           'currentScript': currentScriptAccess,
           'mainCallClosure': mainCallClosure
         });
   }
 }