Add ClosedWorld.elementEnvironment and remove Compiler.elementEnvironment

tests/compiler/dart2js/kernel/closed_world_test.dart

 // Copyright (c) 2016, 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.
 
 // Tests that the closed world computed from [WorldImpact]s derived from kernel
 // is equivalent to the original computed from resolution.
 library dart2js.kernel.closed_world_test;
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
@@ skipping 94 matching lines @@
         new ElementResolutionWorldBuilder(
             backend,
             compiler.resolution,
             backend.nativeBasicData,
             backend.nativeDataBuilder,
             interceptorDataBuilder,
             backendUsageBuilder,
             const OpenWorldStrategy()),
         new KernelTestWorkItemBuilder(compiler),
         'enqueuer from kernel');
-    ClosedWorld closedWorld = computeClosedWorld(
-        compiler.reporter, enqueuer, compiler.elementEnvironment);
+    ClosedWorld closedWorld = computeClosedWorld(compiler.reporter, enqueuer,
+        compiler.frontendStrategy.elementEnvironment);
     BackendUsage backendUsage = backendUsageBuilder.close();
     checkResolutionEnqueuers(
         backendUsage, backendUsage, compiler.enqueuer.resolution, enqueuer,
         typeEquivalence: (ResolutionDartType a, ResolutionDartType b) {
       return areTypesEquivalent(unalias(a), unalias(b));
     },
         elementFilter: elementFilter,
         verbose: arguments.verbose,
         // TODO(johnniwinther): Support class usage testing in presence of
         // redirecting constructors.
         skipClassUsageTesting: true);
     checkClosedWorlds(
         compiler.resolutionWorldBuilder.closedWorldForTesting, closedWorld,
         verbose: arguments.verbose);
   });
 }
 
 List createResolutionEnqueuerListener(Compiler compiler) {
   JavaScriptBackend backend = compiler.backend;
   BackendUsageBuilder backendUsageBuilder =
       new BackendUsageBuilderImpl(compiler.frontendStrategy.commonElements);
   InterceptorDataBuilder interceptorDataBuilder =
       new InterceptorDataBuilderImpl(
           backend.nativeBasicData,
-          compiler.elementEnvironment,
+          compiler.frontendStrategy.elementEnvironment,
           compiler.frontendStrategy.commonElements);
   ResolutionEnqueuerListener listener = new ResolutionEnqueuerListener(
       compiler.options,
       compiler.frontendStrategy.elementEnvironment,
       compiler.frontendStrategy.commonElements,
       backend.impacts,
       backend.nativeBasicData,
       interceptorDataBuilder,
       backendUsageBuilder,
       backend.rtiNeedBuilder,
@@ skipping 14 matching lines @@
 
 ClosedWorld computeClosedWorld(DiagnosticReporter reporter,
     ResolutionEnqueuer enqueuer, ElementEnvironment elementEnvironment) {
   enqueuer.open(const ImpactStrategy(), elementEnvironment.mainFunction,
       elementEnvironment.libraries);
   enqueuer.forEach((WorkItem work) {
     enqueuer.applyImpact(work.run(), impactSource: work.element);
   });
   return enqueuer.worldBuilder.closeWorld();
 }