Implement JsKernelToElementMap through KernelToElementMapBase

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 16 matching lines @@
 import '../universe/class_set.dart';
 import '../universe/world_builder.dart';
 import '../util/emptyset.dart';
 import '../world.dart';
 import 'closure.dart';
 import 'elements.dart';
 import 'locals.dart';
 
 class JsBackendStrategy implements KernelBackendStrategy {
   final Compiler _compiler;
-  final JsToFrontendMap _map = new JsToFrontendMapImpl();
   ElementEnvironment _elementEnvironment;
   CommonElements _commonElements;
-  KernelToElementMapForBuilding _elementMap;
+  JsKernelToElementMap _elementMap;
   ClosureConversionTask _closureDataLookup;
   final GlobalLocalsMap _globalLocalsMap = new GlobalLocalsMap();
   Sorter _sorter;
 
   JsBackendStrategy(this._compiler);
 
   KernelToElementMapForBuilding get elementMap {
-    if (_elementMap == null) {
-      KernelFrontEndStrategy strategy = _compiler.frontendStrategy;
-      KernelToElementMapForImpact elementMap = strategy.elementMap;
-      _elementMap = new JsKernelToElementMap(
-          _compiler.reporter,
-          _compiler.environment,
-          _map,
-          _elementEnvironment,
-          _commonElements,
-          elementMap);
-    }
+    assert(_elementMap != null,
+        "JsBackendStrategy.elementMap has not been created yet.");
     return _elementMap;
   }
 
   GlobalLocalsMap get globalLocalsMapForTesting => _globalLocalsMap;
 
   @override
   ClosedWorldRefiner createClosedWorldRefiner(ClosedWorld closedWorld) {
-    _elementEnvironment =
-        new JsElementEnvironment(_map, closedWorld.elementEnvironment);
-    _commonElements = new JsCommonElements(_map, closedWorld.commonElements);
+    KernelFrontEndStrategy strategy = _compiler.frontendStrategy;
+    KernelToElementMapForImpact elementMap = strategy.elementMap;
+    _elementMap = new JsKernelToElementMap(
+        _compiler.reporter, _compiler.environment, elementMap);
+    _elementEnvironment = _elementMap.elementEnvironment;
+    _commonElements = _elementMap.commonElements;
+    JsToFrontendMap _map = _elementMap.jsToFrontendMap;
     BackendUsage backendUsage =
         new JsBackendUsage(_map, closedWorld.backendUsage);
     NativeData nativeData = new JsNativeData(_map, closedWorld.nativeData);
     InterceptorData interceptorData = new InterceptorDataImpl(
         nativeData,
         _commonElements,
         // TODO(johnniwinther): Convert these.
         const {},
         new Set(),
         new Set());
@@ skipping 85 matching lines @@
       ClosedWorld closedWorld,
       SelectorConstraintsStrategy selectorConstraintsStrategy) {
     return new KernelCodegenWorldBuilder(
         elementMap,
         closedWorld.elementEnvironment,
         nativeBasicData,
         closedWorld,
         selectorConstraintsStrategy);
   }
 }