Refactoring to prepare for kernel based jump targets

pkg/compiler/lib/src/js_backend/backend_usage.dart

 // Copyright (c) 2017, 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.
 
 import '../common.dart';
 import '../common_elements.dart';
 import '../elements/elements.dart' show Element;
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../util/util.dart' show Setlet;
@@ skipping 136 matching lines @@
                   .contains('_internal/js_runtime/lib/')) ||
           element.library == _commonElements.jsHelperLibrary ||
           element.library == _commonElements.interceptorsLibrary ||
           element.library == _commonElements.isolateHelperLibrary) {
         // TODO(johnniwinther): We should be more precise about these.
         return true;
       } else {
         return false;
       }
     }
-    // TODO(johnniwinther): Support remaining checks on [Entity]s.
+    // TODO(redemption): Support remaining checks on [Entity]s.
     return true;
   }
 
   bool _isValidEntity(Entity element) {
     if (element is ConstructorEntity &&
         (element == _commonElements.streamIteratorConstructor ||
             _commonElements.isSymbolConstructor(element) ||
             _commonElements.isSymbolValidatedConstructor(element) ||
             element == _commonElements.syncCompleterConstructor)) {
       // TODO(johnniwinther): These are valid but we could be more precise.
@@ skipping 174 matching lines @@
       _globalFunctionDependencies ?? const <FunctionEntity>[];
 
   @override
   Iterable<ClassEntity> get globalClassDependencies =>
       _globalClassDependencies ?? const <ClassEntity>[];
 
   Iterable<FunctionEntity> get helperFunctionsUsed => _helperFunctionsUsed;
 
   Iterable<ClassEntity> get helperClassesUsed => _helperClassesUsed;
 }