Add comments to vectors/hash sets of raw pointers to on-heap objects used in webaudio/

Source/modules/webaudio/AudioNodeInput.h

 /*
  * Copyright (C) 2010, 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:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 69 matching lines @@
     unsigned numberOfChannels() const;
 
 private:
     explicit AudioNodeInput(AudioNode&);
 
     RawPtrWillBeMember<AudioNode> m_node;
 
     // m_disabledOutputs contains the AudioNodeOutputs which are disabled (will not be processed) by the audio graph rendering.
     // But, from JavaScript's perspective, these outputs are still connected to us.
     // Generally, these represent disabled connections from "notes" which have finished playing but are not yet garbage collected.
+    // Oilpan: Since items are added to the hash set by the audio thread (not registered to Oilpan),
+    // we cannot use a HeapHashSet.
     HashSet<AudioNodeOutput*> m_disabledOutputs;
 
     // Called from context's audio thread.
     AudioBus* internalSummingBus();
     void sumAllConnections(AudioBus* summingBus, size_t framesToProcess);
 
     RefPtr<AudioBus> m_internalSummingBus;
 };
 
 } // namespace blink
 
 #endif // AudioNodeInput_h