- Add assertions in MutexLocker/MonitorLocker to ensure that the code enclosed

runtime/vm/thread_test.cc

Index: runtime/vm/thread_test.cc
diff --git a/runtime/vm/thread_test.cc b/runtime/vm/thread_test.cc
index 95ea190c71d7a002aca2b87d04e6c9871f6b7ef6..314af0dc491fe19185e53dffcaba420ef411f89d 100644
--- a/runtime/vm/thread_test.cc
+++ b/runtime/vm/thread_test.cc
@@ -44,6 +44,9 @@ UNIT_TEST_CASE(Monitor) {
   thread->DisableThreadInterrupts();
   Monitor* monitor = new Monitor();
   monitor->Enter();
+  EXPECT_EQ(false, monitor->TryEnter());
+  monitor->Exit();
+  EXPECT_EQ(true, monitor->TryEnter());
   monitor->Exit();
 
   const int kNumAttempts = 5;