Fix top level type inference in the event that there are circularities.

pkg/front_end/testcases/inference/circular_reference_via_closures_initializer_types.dart.strong.expect

Index: pkg/front_end/testcases/inference/circular_reference_via_closures_initializer_types.dart.strong.expect
diff --git a/pkg/front_end/testcases/inference/circular_reference_via_closures_initializer_types.dart.strong.expect b/pkg/front_end/testcases/inference/circular_reference_via_closures_initializer_types.dart.strong.expect
new file mode 100644
index 0000000000000000000000000000000000000000..fd3ef5ec1bf8284d53dd8d5bed1d1dc874b231be
--- /dev/null
+++ b/pkg/front_end/testcases/inference/circular_reference_via_closures_initializer_types.dart.strong.expect
@@ -0,0 +1,6 @@
+library test;
+import self as self;
+
+static field dynamic x = () → dynamic => self::y;
+static field dynamic y = () → dynamic => self::x;
+static method main() → dynamic {}