Web MIDI: call AccumulateMidiBytesSent() after operation finished

media/midi/midi_manager.h

Index: media/midi/midi_manager.h
diff --git a/media/midi/midi_manager.h b/media/midi/midi_manager.h
index a7c5262d8fd9f8c79dc45d0b61b99bf3e54f96e9..2904c117a1f10d790fc431a3a59d10107868ab47 100644
--- a/media/midi/midi_manager.h
+++ b/media/midi/midi_manager.h
@@ -86,6 +86,10 @@ class MEDIA_EXPORT MidiManager {
   // A client calls EndSession() to stop receiving MIDI data.
   void EndSession(MidiManagerClient* client);
 
+  // Invoke AccumulateMidiBytesSent() for |client| safely. If the session was
+  // already closed, do nothing.
+  void AccumulateMidiBytesSent(MidiManagerClient* client, size_t n);
+
   // DispatchSendMidiData() is called when MIDI data should be sent to the MIDI
   // system.
   // This method is supposed to return immediately and should not block.