Decouple MIDIAccess initialization from MIDIAccess class.

Source/modules/webmidi/MIDIAccessor.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 30 matching lines @@
 class MIDIAccessorClient;
 
 class MIDIAccessor FINAL : public blink::WebMIDIAccessorClient {
 public:
     static PassOwnPtr<MIDIAccessor> create(MIDIAccessorClient*);
 
     virtual ~MIDIAccessor() { }
 
     void startSession();
     void sendMIDIData(unsigned portIndex, const unsigned char* data, size_t length, double timeStamp);
+    // MIDIAccessInitializer and MIDIAccess are both MIDIAccessClient.
+    // MIDIAccessInitializer is the first client and MIDIAccess takes over it
+    // once the initialization successfully finishes.
+    void setClient(MIDIAccessorClient* client) { m_client = client; }
 
     // blink::WebMIDIAccessorClient
     virtual void didAddInputPort(const blink::WebString& id, const blink::WebString& manufacturer, const blink::WebString& name, const blink::WebString& version) OVERRIDE;
     virtual void didAddOutputPort(const blink::WebString& id, const blink::WebString& manufacturer, const blink::WebString& name, const blink::WebString& version) OVERRIDE;
     virtual void didStartSession(bool success, const blink::WebString& error, const blink::WebString& message) OVERRIDE;
     virtual void didReceiveMIDIData(unsigned portIndex, const unsigned char* data, size_t length, double timeStamp) OVERRIDE;
 
 private:
     explicit MIDIAccessor(MIDIAccessorClient*);
 
     MIDIAccessorClient* m_client;
     OwnPtr<blink::WebMIDIAccessor> m_accessor;
 };
 
 } // namespace WebCore
 
 #endif // MIDIAccessor_h