Oilpan: eagerly finalize MIDIAccess.

Source/modules/webmidi/MIDIAccess.h

Index: Source/modules/webmidi/MIDIAccess.h
diff --git a/Source/modules/webmidi/MIDIAccess.h b/Source/modules/webmidi/MIDIAccess.h
index a91fadd4fae6a52174e38bd5d7f1dc3d9c506b07..0dec3ee0d7240fc340b53d4c0faf425fb369291f 100644
--- a/Source/modules/webmidi/MIDIAccess.h
+++ b/Source/modules/webmidi/MIDIAccess.h
@@ -93,6 +93,10 @@ public:
     // |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: