Extract ResolutionWorldBuilderBase from ElementResolutionWorldBuilder

tests/compiler/dart2js/instantiated_classes_test.dart

Index: tests/compiler/dart2js/instantiated_classes_test.dart
diff --git a/tests/compiler/dart2js/instantiated_classes_test.dart b/tests/compiler/dart2js/instantiated_classes_test.dart
index 35232dbfb5806aebd8363160f6233d4228bf1dec..b270135bad8ddf95f8f3e89390038e7eaf350c11 100644
--- a/tests/compiler/dart2js/instantiated_classes_test.dart
+++ b/tests/compiler/dart2js/instantiated_classes_test.dart
@@ -7,7 +7,7 @@ library instantiated_classes_test;
 import 'dart:async';
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
-import 'package:compiler/src/elements/elements.dart' show ClassElement;
+import 'package:compiler/src/elements/entities.dart' show ClassEntity;
 import 'type_test_helper.dart';
 
 void main() {
@@ -90,9 +90,9 @@ Future test(String source, List<String> directlyInstantiatedClasses,
   return TypeEnvironment
       .create(source, mainSource: mainSource.toString(), useMockCompiler: true)
       .then((env) {
-    Iterable<ClassElement> expectedClasses =
+    Iterable<ClassEntity> expectedClasses =
         directlyInstantiatedClasses.map(env.getElement);
-    Iterable<ClassElement> actualClasses = env
+    Iterable<ClassEntity> actualClasses = env
         .compiler.resolutionWorldBuilder.directlyInstantiatedClasses
         .where((c) => c.library == env.compiler.mainApp);
     Expect.setEquals(expectedClasses, actualClasses);