Add tests for `FutureOr<T>`.

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index 2e7457fb913a564390fd8f7fb5a69115e765b8e3..d81da080ac65cb68d3f7f9a180537b48b4896e54 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -8,6 +8,12 @@ mirrors/redirecting_factory_different_type_test: SkipByDesign # Tests type check
 [ $compiler == dart2js ]
 async/schedule_microtask6_test: RuntimeError # global error handling is not supported. Issue 5958
 
+async/future_or_bad_type_test/00: RuntimeError # Issue 28011
+async/future_or_bad_type_test/01: RuntimeError # Issue 28011
+async/future_or_bad_type_test/implements: MissingCompileTimeError # Issue 28011
+async/future_or_non_strong_test: RuntimeError # Issue 28011
+async/future_or_strong_test: RuntimeError, OK
+
 math/double_pow_test: RuntimeError
 math/low_test: RuntimeError
 math/random_big_test: RuntimeError  # Using bigint seeds for random.