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

tests/lib/typed_data/float32x4_sign_mask_test.dart

Index: tests/lib/typed_data/float32x4_sign_mask_test.dart
diff --git a/tests/lib/typed_data/float32x4_sign_mask_test.dart b/tests/lib/typed_data/float32x4_sign_mask_test.dart
index 95825d4a3b7cf374a6229ab6fa51733ada4d19c9..06a0bb0e3b409a4e901bdbbd0d3dda6dd0a32afd 100644
--- a/tests/lib/typed_data/float32x4_sign_mask_test.dart
+++ b/tests/lib/typed_data/float32x4_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 float32x4_sign_mask;