Add ClosedWorld.elementEnvironment and remove Compiler.elementEnvironment

tests/compiler/dart2js/kernel/closed_world_test.dart

Index: tests/compiler/dart2js/kernel/closed_world_test.dart
diff --git a/tests/compiler/dart2js/kernel/closed_world_test.dart b/tests/compiler/dart2js/kernel/closed_world_test.dart
index d8464eaddbae02eec4cf1373afc16347c023c621..fc918140ea2ff01cc49c06a337cfbe8927de9bf9 100644
--- a/tests/compiler/dart2js/kernel/closed_world_test.dart
+++ b/tests/compiler/dart2js/kernel/closed_world_test.dart
@@ -112,8 +112,8 @@ main(List<String> args) {
             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,
@@ -138,7 +138,7 @@ List createResolutionEnqueuerListener(Compiler compiler) {
   InterceptorDataBuilder interceptorDataBuilder =
       new InterceptorDataBuilderImpl(
           backend.nativeBasicData,
-          compiler.elementEnvironment,
+          compiler.frontendStrategy.elementEnvironment,
           compiler.frontendStrategy.commonElements);
   ResolutionEnqueuerListener listener = new ResolutionEnqueuerListener(
       compiler.options,