Reapply "Added for-loop variable tracking and regular closures/initializers captured variable track…

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 45 matching lines @@
       covariant ClosedWorldBase closedWorld) {
     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);
+    _closureDataLookup = new KernelClosureConversionTask(
+        _compiler.measurer, _elementMap, _map, _globalLocalsMap);
     NativeData nativeData = new JsNativeData(_map, closedWorld.nativeData);
     InterceptorData interceptorData = new InterceptorDataImpl(
         nativeData,
         _commonElements,
         // TODO(johnniwinther): Convert these.
         const {},
         new Set(),
         new Set());
 
     Map<ClassEntity, ClassHierarchyNode> classHierarchyNodes =
@@ skipping 68 matching lines @@
         allTypedefs: new ImmutableEmptySet<TypedefElement>(),
         typesImplementedBySubclasses: null);
   }
 
   @override
   Sorter get sorter {
     return _sorter ??= new KernelSorter(elementMap);
   }
 
   @override
-  ClosureConversionTask get closureDataLookup =>
-      _closureDataLookup ??= new KernelClosureConversionTask(
-          _compiler.measurer, elementMap, _globalLocalsMap);
+  ClosureConversionTask get closureDataLookup => _closureDataLookup;
 
   @override
   SourceInformationStrategy get sourceInformationStrategy =>
       const JavaScriptSourceInformationStrategy();
 
   @override
   SsaBuilder createSsaBuilder(CompilerTask task, JavaScriptBackend backend,
       SourceInformationStrategy sourceInformationStrategy) {
     return new KernelSsaBuilder(
         task, backend.compiler, elementMap, _globalLocalsMap);
@@ skipping 10 matching lines @@
       ClosedWorld closedWorld,
       SelectorConstraintsStrategy selectorConstraintsStrategy) {
     return new KernelCodegenWorldBuilder(
         elementMap,
         closedWorld.elementEnvironment,
         nativeBasicData,
         closedWorld,
         selectorConstraintsStrategy);
   }
 }