Fix use after free in HWNDMessageHandler

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index d726ea930d98d95feceb2da247503f41c5fabb27..f589c84dee2f2385e87388c91674f22aa75212cc 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -1452,8 +1452,11 @@ LRESULT HWNDMessageHandler::OnImeMessages(UINT message,
                                           WPARAM w_param,
                                           LPARAM l_param) {
   LRESULT result = 0;
-  SetMsgHandled(delegate_->HandleIMEMessage(
-      message, w_param, l_param, &result));
+  base::WeakPtr<HWNDMessageHandler> ref(weak_factory_.GetWeakPtr());
+  const bool msg_handled =
+      delegate_->HandleIMEMessage(message, w_param, l_param, &result);
+  if (ref.get())
+    SetMsgHandled(msg_handled);
   return result;
 }