Add ClosedWorld.elementEnvironment and remove Compiler.elementEnvironment

pkg/compiler/lib/src/js_backend/element_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_backend.element_strategy;
 
 import '../backend_strategy.dart';
 import '../common.dart';
 import '../common/codegen.dart';
 import '../common/work.dart';
@@ skipping 32 matching lines @@
 
   void convertClosures(ClosedWorldRefiner closedWorldRefiner) {
     _compiler.closureToClassMapper.createClosureClasses(closedWorldRefiner);
   }
 
   @override
   CodegenWorldBuilder createCodegenWorldBuilder(
       NativeBasicData nativeBasicData,
       ClosedWorld closedWorld,
       SelectorConstraintsStrategy selectorConstraintsStrategy) {
-    return new ElementCodegenWorldBuilderImpl(_compiler.elementEnvironment,
+    return new ElementCodegenWorldBuilderImpl(closedWorld.elementEnvironment,
         nativeBasicData, closedWorld, selectorConstraintsStrategy);
   }
 
   @override
   WorkItemBuilder createCodegenWorkItemBuilder(ClosedWorld closedWorld) {
     return new ElementCodegenWorkItemBuilder(
         _compiler.backend, closedWorld, _compiler.options);
   }
 
   @override
@@ skipping 89 matching lines @@
 
   MemberElement get element => resolvedAst.element;
 
   WorldImpact run() {
     registry = new CodegenRegistry(element);
     return _backend.codegen(this, _closedWorld);
   }
 
   String toString() => 'CodegenWorkItem(${resolvedAst.element})';
 }