Fix byte_array_test to work in checked mode.

tests/standalone/byte_array_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Dart test program for testing native byte arrays.
 
 // Library tag to be able to run in html test framework.
 #library("ByteArrayTest.dart");
 
 #import('dart:scalarlist');
@@ skipping 89 matching lines @@
   testThrowsIndex(() => array.subByteArray(0, -1));
   testThrowsIndex(() => array.subByteArray(1, -1));
   testThrowsIndex(() => array.subByteArray(10, -1));
   testThrowsIndex(() => array.subByteArray(-1, 0));
   testThrowsIndex(() => array.subByteArray(-1));
   testThrowsIndex(() => array.subByteArray(-1, null));
   testThrowsIndex(() => array.subByteArray(11, 0));
   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);
 }
 
 main() {
   for (int i = 0; i < 2000; i++) {
     testCreateByteArray();
     testSetRange();
     testIndexOutOfRange();
     testIndexOf();
     testSubArray();
   }
 }