Web MIDI: fix multi-threading problem around message buffer handling

content/renderer/media/midi_message_filter.cc

Index: content/renderer/media/midi_message_filter.cc
diff --git a/content/renderer/media/midi_message_filter.cc b/content/renderer/media/midi_message_filter.cc
index 39f391494f00a24a99fdb89ba3270d1edbb55e65..b3d527a89d8e8f70deb45c589ea2777ae0efc76b 100644
--- a/content/renderer/media/midi_message_filter.cc
+++ b/content/renderer/media/midi_message_filter.cc
@@ -187,7 +187,7 @@ void MIDIMessageFilter::HandleDataReceived(int port,
 #endif
 }
 
-void MIDIMessageFilter::SendMIDIData(int port,
+void MIDIMessageFilter::SendMIDIData(unsigned int port,
                                      const uint8* data,
                                      size_t length,
                                      double timestamp) {
@@ -203,7 +203,7 @@ void MIDIMessageFilter::SendMIDIData(int port,
                  port, v, timestamp));
 }
 
-void MIDIMessageFilter::SendMIDIDataOnIOThread(int port,
+void MIDIMessageFilter::SendMIDIDataOnIOThread(unsigned int port,
                                                const std::vector<uint8>& data,
                                                double timestamp) {
   size_t n = data.size();