Support serialization of WorldImpact

pkg/compiler/lib/src/js_backend/js_backend.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 js_backend;
 
 import 'dart:async' show EventSink, Future;
 import 'dart:collection' show HashMap;
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
 import 'package:js_runtime/shared/embedded_names.dart' show JsGetName;
 
 import '../closure.dart';
 import '../common.dart';
 import '../common/backend_api.dart' show
     Backend,
+    BackendSerialization,
     ImpactTransformer,
     ForeignResolver;
 import '../common/codegen.dart' show
     CodegenImpact,
     CodegenRegistry,
     CodegenWorkItem;
 import '../common/names.dart' show
     Identifiers,
     Names,
     Selectors,
@@ skipping 82 matching lines @@
     TransformedWorldImpact,
     WorldImpact,
     WorldImpactVisitor;
 import '../util/characters.dart';
 import '../util/util.dart';
 import '../world.dart' show
     ClassWorld;
 
 import 'backend_helpers.dart';
 import 'backend_impact.dart';
+import 'backend_serialization.dart' show
+    JavaScriptBackendSerialization;
 import 'codegen/task.dart';
 import 'constant_system_javascript.dart';
-import 'patch_resolver.dart';
+import 'native_data.dart' show
+    NativeData;
 import 'js_interop_analysis.dart' show JsInteropAnalysis;
 import 'lookup_map_analysis.dart' show LookupMapAnalysis;
+import 'patch_resolver.dart';
 
 part 'backend.dart';
 part 'checked_mode_helpers.dart';
 part 'constant_emitter.dart';
 part 'constant_handler_javascript.dart';
 part 'custom_elements_analysis.dart';
 part 'frequency_namer.dart';
 part 'field_naming_mixin.dart';
 part 'minify_namer.dart';
 part 'namer.dart';
 part 'namer_names.dart';
 part 'no_such_method_registry.dart';
 part 'runtime_types.dart';
 part 'type_variable_handler.dart';