Fix file descriptor leak in event handler implementation. When shutting down an isolate, we did not…

runtime/platform/thread_win.h

Index: runtime/platform/thread_win.h
diff --git a/runtime/platform/thread_win.h b/runtime/platform/thread_win.h
index b481cec0f63dc5b11967e197763d9ac186559ac9..b67b25431950514c82671de9bc6c860fd412afcc 100644
--- a/runtime/platform/thread_win.h
+++ b/runtime/platform/thread_win.h
@@ -49,8 +49,15 @@ class MutexData {
 
 
 class MonitorWaitData {
+ public:
+  static void ThreadExit();
+
  private:
   explicit MonitorWaitData(HANDLE event) : event_(event), next_(NULL) {}
+  ~MonitorWaitData() {
+    CloseHandle(event_);
+    ASSERT(next_ == NULL);
+  }
 
   // ThreadLocalKey used to fetch and store the MonitorWaitData object
   // for a given thread.