Use [ClassElement.isSubclassOf] instead of [World.isSubClassOf].

pkg/compiler/lib/src/js_emitter/type_test_generator.dart

Index: pkg/compiler/lib/src/js_emitter/type_test_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/type_test_generator.dart b/pkg/compiler/lib/src/js_emitter/type_test_generator.dart
index 5ff5e0071ae2ec53e41fa8566c2a295be6037a0e..60ae6f005805499e7b5352b228b2971c900f9bbd 100644
--- a/pkg/compiler/lib/src/js_emitter/type_test_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/type_test_generator.dart
@@ -64,7 +64,7 @@ class TypeTestGenerator {
     /// TODO(herhut): Generate tests for native classes dynamically, as well.
     void generateIsTest(Element other) {
       if (classElement.isNative ||
-          !compiler.world.isSubclassOf(classElement, other)) {
+          !classElement.isSubclassOf(other)) {
         result.properties[namer.operatorIs(other)] = js('1');
       }
     }