Web MIDI: implement implicit open() on send() and setOnmidimessage()

Source/modules/webmidi/MIDIInput.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 27 matching lines @@
 namespace blink {
 
 class MIDIAccess;
 
 class MIDIInput final : public MIDIPort {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static MIDIInput* create(MIDIAccess*, const String& id, const String& manufacturer, const String& name, const String& version, MIDIAccessor::MIDIPortState);
     virtual ~MIDIInput() { }
 
-    DEFINE_ATTRIBUTE_EVENT_LISTENER(midimessage);
+    EventListener* onmidimessage();
+    void setOnmidimessage(PassRefPtr<EventListener>);
 
     // EventTarget
     virtual const AtomicString& interfaceName() const override { return EventTargetNames::MIDIInput; }
 
     // |timeStamp| is a DOMHighResTimeStamp in the time coordinate system of performance.now().
     void didReceiveMIDIData(unsigned portIndex, const unsigned char* data, size_t length, double timeStamp);
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     MIDIInput(MIDIAccess*, const String& id, const String& manufacturer, const String& name, const String& version, MIDIAccessor::MIDIPortState);
 };
 
 } // namespace blink
 
 #endif // MIDIInput_h