- Do not repeatedly allocate and release Monitor objects.

runtime/vm/isolate_test.cc

Index: runtime/vm/isolate_test.cc
diff --git a/runtime/vm/isolate_test.cc b/runtime/vm/isolate_test.cc
index ef3ba53a63af1b0c96b069d945a3d4a623005451..6491c41da9310689d883161c58667cfe99f35023 100644
--- a/runtime/vm/isolate_test.cc
+++ b/runtime/vm/isolate_test.cc
@@ -131,7 +131,9 @@ const intptr_t InterruptChecker::kIterations = 10;
 // round update *before* the interrupt is set.
 TEST_CASE(StackLimitInterrupts) {
   Isolate* isolate = Thread::Current()->isolate();
-  ThreadBarrier barrier(InterruptChecker::kTaskCount + 1);
+  ThreadBarrier barrier(InterruptChecker::kTaskCount + 1,
+                        isolate->heap()->barrier(),
+                        isolate->heap()->barrier_done());
   // Start all tasks. They will busy-wait until interrupted in the first round.
   for (intptr_t task = 0; task < InterruptChecker::kTaskCount; task++) {
     Dart::thread_pool()->Run(new InterruptChecker(isolate, &barrier));