Fix byte_array_test to work in checked mode.

tests/standalone/byte_array_test.dart

Index: tests/standalone/byte_array_test.dart
diff --git a/tests/standalone/byte_array_test.dart b/tests/standalone/byte_array_test.dart
index 11bccddb661fa517078e41cee997fd76e2502776..1565488ace4ed4c9adc3961b22f1067292be9c6e 100644
--- a/tests/standalone/byte_array_test.dart
+++ b/tests/standalone/byte_array_test.dart
@@ -107,9 +107,15 @@ void testSubArray() {
   testThrowsIndex(() => array.subByteArray(11));
   testThrowsIndex(() => array.subByteArray(11, null));
   testThrowsIndex(() => array.subByteArray(6, 5));
-  Expect.throws(() => array.subByteArray(0, "5"), (e) => e is ArgumentError);
-  Expect.throws(() => array.subByteArray("0", 5), (e) => e is ArgumentError);
-  Expect.throws(() => array.subByteArray("0"), (e) => e is ArgumentError);
+
+  bool checkedMode = false;
+  assert(checkedMode = true);
+  if (!checkedMode) {
+    // In checked mode these will necessarily throw a TypeError.
+    Expect.throws(() => array.subByteArray(0, "5"), (e) => e is ArgumentError);
+    Expect.throws(() => array.subByteArray("0", 5), (e) => e is ArgumentError);
+    Expect.throws(() => array.subByteArray("0"), (e) => e is ArgumentError);
+  }
   Expect.throws(() => array.subByteArray(null), (e) => e is ArgumentError);
 }