Make corelib_strong tests strong-mode compliant

tests/corelib_strong/list_fill_range_test.dart

Index: tests/corelib_strong/list_fill_range_test.dart
diff --git a/tests/corelib_strong/list_fill_range_test.dart b/tests/corelib_strong/list_fill_range_test.dart
index 4553e430afc0c54398e7ab225cac59a80f7f1801..5051d9cf1642ec739cf6a4c24dd7b6621100a324 100644
--- a/tests/corelib_strong/list_fill_range_test.dart
+++ b/tests/corelib_strong/list_fill_range_test.dart
@@ -65,10 +65,10 @@ main() {
   expectUE(() => test(const [1, 2, 3], 1, 4));
 }
 
-void expectRE(Function f) {
+void expectRE(void f()) {
   Expect.throws(f, (e) => e is RangeError);
 }
 
-void expectUE(Function f) {
+void expectUE(void f()) {
   Expect.throws(f, (e) => e is UnsupportedError);
 }