Split implementation of KernelToElementMapImpl

pkg/compiler/lib/src/js_model/js_strategy.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.
 
 library dart2js.js_model.strategy;
 
 import '../closure.dart' show ClosureConversionTask;
 import '../common/tasks.dart';
 import '../common_elements.dart';
 import '../compiler.dart';
@@ skipping 22 matching lines @@
 import 'locals.dart';
 
 class JsBackendStrategy implements KernelBackendStrategy {
   final Compiler _compiler;
   final JsToFrontendMap _map = new JsToFrontendMapImpl();
   ElementEnvironment _elementEnvironment;
   CommonElements _commonElements;
   KernelToElementMapForBuilding _elementMap;
   ClosureConversionTask _closureDataLookup;
   final GlobalLocalsMap _globalLocalsMap = new GlobalLocalsMap();
+  Sorter _sorter;
 
   JsBackendStrategy(this._compiler);
 
   KernelToElementMapForBuilding get elementMap {
     if (_elementMap == null) {
       KernelFrontEndStrategy strategy = _compiler.frontendStrategy;
-      KernelToElementMapForBuilding elementMap = strategy.elementMap;
+      KernelToElementMapForImpact elementMap = strategy.elementMap;
       _elementMap = new JsKernelToElementMap(
           _compiler.reporter,
           _compiler.environment,
           _map,
           _elementEnvironment,
           _commonElements,
           elementMap);
     }
     return _elementMap;
   }
@@ skipping 66 matching lines @@
         interceptorData: interceptorData,
         classHierarchyNodes: classHierarchyNodes,
         classSets: classSets,
         implementedClasses: implementedClasses,
         // TODO(johnniwinther): Support this.
         allTypedefs: new ImmutableEmptySet<TypedefElement>());
   }
 
   @override
   Sorter get sorter {
-    throw new UnimplementedError('JsBackendStrategy.sorter');
+    return _sorter ??= new KernelSorter(elementMap);
   }
 
   @override
   ClosureConversionTask get closureDataLookup =>
       _closureDataLookup ??= new KernelClosureConversionTask(
           _compiler.measurer, elementMap, _globalLocalsMap);
 
   @override
   SourceInformationStrategy get sourceInformationStrategy =>
       const JavaScriptSourceInformationStrategy();
@@ skipping 16 matching lines @@
       ClosedWorld closedWorld,
       SelectorConstraintsStrategy selectorConstraintsStrategy) {
     return new KernelCodegenWorldBuilder(
         elementMap,
         closedWorld.elementEnvironment,
         nativeBasicData,
         closedWorld,
         selectorConstraintsStrategy);
   }
 }