Turn off background compilation when running with --verify_gc, since the background compilation con…

tests/lib/convert/streamed_conversion_json_utf8_decode_test.dart

Index: tests/lib/convert/streamed_conversion_json_utf8_decode_test.dart
diff --git a/tests/lib/convert/streamed_conversion_json_utf8_decode_test.dart b/tests/lib/convert/streamed_conversion_json_utf8_decode_test.dart
index 52a8005216af63bdd195c5adbe1010a11d373920..ab014ee598c45252ca8cf08dfdd5cff1bc8fe0e3 100644
--- a/tests/lib/convert/streamed_conversion_json_utf8_decode_test.dart
+++ b/tests/lib/convert/streamed_conversion_json_utf8_decode_test.dart
@@ -2,7 +2,7 @@
 // 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.
 // Test write barrier verification mode.
-// VMOptions=--verify_before_gc --verify_after_gc --old_gen_growth_rate=1
+// VMOptions=--verify_before_gc --verify_after_gc --old_gen_growth_rate=1 --no-background-compilation
 // VMOptions=
 
 import "package:expect/expect.dart";