Revert of WebAudio: Remove AudioNode::RefType.

Source/modules/webaudio/AudioContext.h

Index: Source/modules/webaudio/AudioContext.h
diff --git a/Source/modules/webaudio/AudioContext.h b/Source/modules/webaudio/AudioContext.h
index ed31ce8b9910eae3fa5643d43b5e2232fed3b51d..2abfa5ca12d0bd9e7073551be932621dc9527fab 100644
--- a/Source/modules/webaudio/AudioContext.h
+++ b/Source/modules/webaudio/AudioContext.h
@@ -267,12 +267,10 @@
     // Only accessed in the audio thread.
     Vector<AudioNode*> m_finishedNodes;
 
-    // List of source nodes. This is either accessed when the graph lock is
-    // held, or on the main thread when the audio thread has finished.
-    // This RefPtr is connection reference. We must call AudioNode::
-    // makeConnection() after ref(), and call AudioNode::breakConnection()
-    // before deref().
-    Vector<RefPtr<AudioNode> > m_referencedNodes;
+    // We don't use RefPtr<AudioNode> here because AudioNode has a more complex ref() / deref() implementation
+    // with an optional argument for refType.  We need to use the special refType: RefTypeConnection
+    // Either accessed when the graph lock is held, or on the main thread when the audio thread has finished.
+    Vector<AudioNode*> m_referencedNodes;
 
     // Accumulate nodes which need to be deleted here.
     // This is copied to m_nodesToDelete at the end of a render cycle in handlePostRenderTasks(), where we're assured of a stable graph