Remove BackendClasses and JavaScriptBackendClasses.

tests/compiler/dart2js/kernel/closed_world_test.dart

 // Copyright (c) 2016, 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.
 
 // Tests that the closed world computed from [WorldImpact]s derived from kernel
 // is equivalent to the original computed from resolution.
 library dart2js.kernel.closed_world_test;
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/closure.dart';
@@ skipping 133 matching lines @@
   });
 }
 
 EnqueuerListener createResolutionEnqueuerListener(Compiler compiler) {
   JavaScriptBackend backend = compiler.backend;
   return new ResolutionEnqueuerListener(
       compiler.options,
       compiler.elementEnvironment,
       compiler.commonElements,
       backend.impacts,
-      backend.backendClasses,
       backend.nativeBasicData,
       backend.interceptorDataBuilder,
       backend.backendUsageBuilder,
       backend.rtiNeedBuilder,
       backend.mirrorsDataBuilder,
       backend.noSuchMethodRegistry,
       backend.customElementsResolutionAnalysis,
       backend.lookupMapResolutionAnalysis,
       backend.mirrorsResolutionAnalysis,
       new TypeVariableResolutionAnalysis(compiler.elementEnvironment,
@@ skipping 31 matching lines @@
   final MemberElement element;
 
   KernelWorkItem(this._compiler, this._impactTransformer, this.element);
 
   @override
   WorldImpact run() {
     ResolutionImpact resolutionImpact = build(_compiler, element.resolvedAst);
     return _impactTransformer.transformResolutionImpact(resolutionImpact);
   }
 }