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

content/renderer/media/midi_message_filter.h

Index: content/renderer/media/midi_message_filter.h
diff --git a/content/renderer/media/midi_message_filter.h b/content/renderer/media/midi_message_filter.h
index cf969e9d8078401a5de3b665b4a0ddfcae4a571f..902d21125f3b3c4139d74096c92ff0cf7dbe4abc 100644
--- a/content/renderer/media/midi_message_filter.h
+++ b/content/renderer/media/midi_message_filter.h
@@ -12,7 +12,6 @@
 #include "content/common/content_export.h"
 #include "ipc/ipc_channel_proxy.h"
 #include "media/midi/midi_port_info.h"
-#include "third_party/WebKit/public/platform/WebMIDIAccessor.h"
 #include "third_party/WebKit/public/platform/WebMIDIAccessorClient.h"
 
 namespace base {
@@ -37,7 +36,7 @@ class CONTENT_EXPORT MIDIMessageFilter
 
   // A client will only be able to call this method if it has a suitable
   // output port (from addOutputPort()).
-  void SendMIDIData(int port,
+  void SendMIDIData(size_t port,
                     const uint8* data,
                     size_t length,
                     double timestamp);
@@ -89,7 +88,7 @@ class CONTENT_EXPORT MIDIMessageFilter
 
   void StartSessionOnIOThread(int client_id);
 
-  void SendMIDIDataOnIOThread(int port,
+  void SendMIDIDataOnIOThread(size_t port,
                               const std::vector<uint8>& data,
                               double timestamp);