src: name scoped lock

Name a scoped lock to be consistent with all the others.

PR-URL: nodejs#50010
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

src/node_messaging.cc

@@ -795,7 +795,7 @@ void MessagePort::OnMessage(MessageProcessingMode mode) {
 
   size_t processing_limit;
   if (mode == MessageProcessingMode::kNormalOperation) {
-    Mutex::ScopedLock(data_->mutex_);
+    Mutex::ScopedLock lock(data_->mutex_);
     processing_limit = std::max(data_->incoming_messages_.size(),
                                 static_cast<size_t>(1000));
   } else {