Add --no-background-compilation to tests that expect to run code in optimized form

tests/lib/typed_data/int32x4_sign_mask_test.dart

Index: tests/lib/typed_data/int32x4_sign_mask_test.dart
diff --git a/tests/lib/typed_data/int32x4_sign_mask_test.dart b/tests/lib/typed_data/int32x4_sign_mask_test.dart
index b4e620ea7385928900e946deec90a6d3525b1d12..522054dece7e9c4573caf9fdf869f927a6fdea31 100644
--- a/tests/lib/typed_data/int32x4_sign_mask_test.dart
+++ b/tests/lib/typed_data/int32x4_sign_mask_test.dart
@@ -1,7 +1,7 @@
 // Copyright (c) 2013, 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.
-// VMOptions=--optimization-counter-threshold=10
+// VMOptions=--optimization-counter-threshold=10 --no-background-compilation
 
 // Library tag to be able to run in html test framework.
 library int32x4_sign_mask;