Rename KernelWorldBuilder to KernelElementBuilder

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 17 matching lines @@
 import 'package:compiler/src/js_backend/native_data.dart';
 import 'package:compiler/src/js_backend/impact_transformer.dart';
 import 'package:compiler/src/js_backend/interceptor_data.dart';
 import 'package:compiler/src/js_backend/lookup_map_analysis.dart';
 import 'package:compiler/src/js_backend/mirrors_analysis.dart';
 import 'package:compiler/src/js_backend/mirrors_data.dart';
 import 'package:compiler/src/js_backend/no_such_method_registry.dart';
 import 'package:compiler/src/js_backend/resolution_listener.dart';
 import 'package:compiler/src/js_backend/type_variable_handler.dart';
 import 'package:compiler/src/native/enqueue.dart';
-import 'package:compiler/src/kernel/world_builder.dart';
+import 'package:compiler/src/kernel/element_builder.dart';
 import 'package:compiler/src/options.dart';
 import 'package:compiler/src/ssa/kernel_impact.dart';
 import 'package:compiler/src/serialization/equivalence.dart';
 import 'package:compiler/src/universe/world_builder.dart';
 import 'package:compiler/src/universe/world_impact.dart';
 import 'package:compiler/src/world.dart';
 import 'package:kernel/ast.dart' as ir;
 import 'impact_test.dart';
 import '../memory_compiler.dart';
 import '../serialization/helper.dart';
@@ skipping 146 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);
   }
 }