Revert "Normalize type masks to use the least upper instantiated subclass/type."

pkg/compiler/lib/src/universe/function_set.dart

Index: pkg/compiler/lib/src/universe/function_set.dart
diff --git a/pkg/compiler/lib/src/universe/function_set.dart b/pkg/compiler/lib/src/universe/function_set.dart
index 9f13c1ea2293b8a2eecbd0fddca6ebbb9be8596b..72a1813e91bc2fd22f13b005e1e6fb6901329c06 100644
--- a/pkg/compiler/lib/src/universe/function_set.dart
+++ b/pkg/compiler/lib/src/universe/function_set.dart
@@ -298,11 +298,8 @@ class FullFunctionSetQuery implements FunctionSetQuery {
         .map((cls) {
           if (classWorld.backend.isNullImplementation(cls)) {
             return const TypeMask.empty();
-          } else if (classWorld.isInstantiated(cls.declaration)) {
-            return new TypeMask.nonNullSubclass(cls.declaration, classWorld);
           } else {
-            // TODO(johnniwinther): Avoid the need for this case.
-            return const TypeMask.empty();
+            return new TypeMask.nonNullSubclass(cls.declaration, classWorld);
           }
         }),
         classWorld);