Fix potential unprotected use of handle in Windows event handler.

runtime/bin/eventhandler_win.cc

Index: runtime/bin/eventhandler_win.cc
diff --git a/runtime/bin/eventhandler_win.cc b/runtime/bin/eventhandler_win.cc
index f9887128c49ef4dae66c19b26a38a1b51555da7b..bd4af3155d92af7e07126b1013e2888ed0069f40 100644
--- a/runtime/bin/eventhandler_win.cc
+++ b/runtime/bin/eventhandler_win.cc
@@ -145,13 +145,13 @@ bool Handle::CreateCompletionPort(HANDLE completion_port) {
 
 
 void Handle::Close() {
+  MonitorLocker ml(monitor_);
   if (!SupportsOverlappedIO()) {
     // If the handle uses synchronous I/O (e.g. stdin), cancel any pending
     // operation before closing the handle, so the read thread is not blocked.
     BOOL result = CancelIoEx(handle_, NULL);
     ASSERT(result || (GetLastError() == ERROR_NOT_FOUND));
   }
-  MonitorLocker ml(monitor_);
   if (!IsClosing()) {
     // Close the socket and set the closing state. This close method can be
     // called again if this socket has pending IO operations in flight.