Fix an undetected Smi overflow on ARM.

tests/language/arithmetic_smi_overflow_test.dart

+// Copyright (c) 2014, 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 to test arithmetic operations.
+
+// VMOptions=--optimization_counter_threshold=5
+
+import "package:expect/expect.dart";
+
+main() {
+  for (var i = 0; i < 10; i++) {
+    Expect.equals(0x40000000, (i - i) - -1073741824);
+    Expect.equals(0x4000000000000000, (i - i) - -4611686018427387904);
+  }
+}