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

content/browser/renderer_host/media/midi_host.cc

Index: content/browser/renderer_host/media/midi_host.cc
diff --git a/content/browser/renderer_host/media/midi_host.cc b/content/browser/renderer_host/media/midi_host.cc
index b0b0e7692f270b4454cb8e26482179dc9b64c040..af09a2260a396b5a9ebaab00ef95a34264dde094 100644
--- a/content/browser/renderer_host/media/midi_host.cc
+++ b/content/browser/renderer_host/media/midi_host.cc
@@ -88,7 +88,7 @@ void MIDIHost::OnStartSession(int client_id) {
        output_ports));
 }
 
-void MIDIHost::OnSendData(int port,
+void MIDIHost::OnSendData(uint32 port,
                           const std::vector<uint8>& data,
                           double timestamp) {
   if (!midi_manager_)
@@ -115,9 +115,8 @@ void MIDIHost::OnSendData(int port,
 
   midi_manager_->DispatchSendMIDIData(
       this,
-      port,
-      &data[0],
-      data.size(),
+      static_cast<size_t>(port),
+      data,
       timestamp);
 
   sent_bytes_in_flight_ += data.size();