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

runtime/vm/os_thread_win.cc

Index: runtime/vm/os_thread_win.cc
diff --git a/runtime/vm/os_thread_win.cc b/runtime/vm/os_thread_win.cc
index 7a29d0da46c27fe457788279a3651f183cd87fb4..ccab0841b3d120ab9fb36611838b76ab042a5073 100644
--- a/runtime/vm/os_thread_win.cc
+++ b/runtime/vm/os_thread_win.cc
@@ -305,6 +305,21 @@ Monitor::~Monitor() {
 }
 
 
+bool Mutex::TryEnter() {
+  // Attempt to pass the semaphore but return immediately.
+  BOOL result = TryEnterCriticalSection(&data_.cs_);
+  if (!result) {
+    return false;
+  }
+#if defined(DEBUG)
+  // When running with assertions enabled we do track the owner.
+  ASSERT(owner_ == OSThread::kInvalidThreadId);
+  owner_ = OSThread::GetCurrentThreadId();
+#endif  // defined(DEBUG)
+  return true;
+}
+
+
 void Monitor::Enter() {
   EnterCriticalSection(&data_.cs_);