Fixed the racy code around the message-only window in base::MessagePumpForUI on Windows.

base/message_loop.cc

Index: base/message_loop.cc
diff --git a/base/message_loop.cc b/base/message_loop.cc
index 0d8a8ef0d769875f386e244b69932779e9ed2271..4289b3c4f5a506087723d03b225f734c54821b9c 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -221,6 +221,9 @@ MessageLoop::~MessageLoop() {
       WillDestroyCurrentMessageLoop();
   message_loop_proxy_ = NULL;
 
+  // Notify the message pump that the message loop is going away.
+  pump_->WillDestroyCurrentMessageLoop();
+
   // OK, now make it so that no one can find us.
   lazy_tls_ptr.Pointer()->Set(NULL);