Mark vm_restart_test Pass, Slow

runtime/observatory/tests/service/service.status

Index: runtime/observatory/tests/service/service.status
diff --git a/runtime/observatory/tests/service/service.status b/runtime/observatory/tests/service/service.status
index 562604a9be666dbb68c4237a999d6f9d0c3a5e11..08d5badab1d6d0b426378b34575b973a5faa7228 100644
--- a/runtime/observatory/tests/service/service.status
+++ b/runtime/observatory/tests/service/service.status
@@ -25,6 +25,9 @@ isolate_lifecycle_test: Pass, RuntimeError # Issue 24174
 debugger_location_second_test: Pass, Slow
 debugger_location_test: Pass, Slow
 
+# Can be slow in debug mode, as well.
+vm_restart_test: Pass, Slow
+
 # These tests are slow on simulators.
 [ $arch == simarm || $arch == simmips || $arch == simarm64 ]
 *: Pass, Slow