Oilpan: eagerly finalize MIDIAccess.

Source/modules/webmidi/MIDIAccess.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 75 matching lines @@
     {
         // This method is for MIDIAccess initialization: MIDIAccessInitializer
         // has the implementation.
         ASSERT_NOT_REACHED();
     }
     void didReceiveMIDIData(unsigned portIndex, const unsigned char* data, size_t length, double timeStamp) override;
 
     // |timeStampInMilliseconds| is in the same time coordinate system as performance.now().
     void sendMIDIData(unsigned portIndex, const unsigned char* data, size_t length, double timeStampInMilliseconds);
 
+    // Eager finalization needed to promptly release m_accessor. Otherwise
+    // its client back reference could end up being unsafely used during
+    // the lazy sweeping phase.
+    EAGERLY_FINALIZE();
     DECLARE_VIRTUAL_TRACE();
 
 private:
     MIDIAccess(PassOwnPtr<MIDIAccessor>, bool sysexEnabled, const Vector<MIDIAccessInitializer::PortDescriptor>&, ExecutionContext*);
 
     OwnPtr<MIDIAccessor> m_accessor;
     bool m_sysexEnabled;
     bool m_hasPendingActivity;
     HeapVector<Member<MIDIInput>> m_inputs;
     HeapVector<Member<MIDIOutput>> m_outputs;
 };
 
 } // namespace blink
 
 #endif // MIDIAccess_h