Revert "Add superclasses, subclasses, and subtypes tracking to the world."

tests/compiler/dart2js/field_type_inferer_test.dart

Index: tests/compiler/dart2js/field_type_inferer_test.dart
diff --git a/tests/compiler/dart2js/field_type_inferer_test.dart b/tests/compiler/dart2js/field_type_inferer_test.dart
index 62c6be0a7bd6a6a27a978b02082c4e3bd2130d7f..04773aa361877e8f31e9ac677c88e9a9c74ce5e5 100644
--- a/tests/compiler/dart2js/field_type_inferer_test.dart
+++ b/tests/compiler/dart2js/field_type_inferer_test.dart
@@ -344,12 +344,7 @@ void doTest(String test, bool disableInlining, Map<String, HType> fields) {
       disableInlining,
       (backend, field) {
         HType inferredType = backend.optimisticFieldType(field);
-        if (type == HType.UNKNOWN) {
-          Expect.isTrue(inferredType == HType.UNKNOWN ||
-                        inferredType.isTop(backend.compiler));
-        } else {
-          Expect.equals(type, inferredType);
-        }
+        Expect.equals(type, inferredType);
     });
   });
 }