Oilpan: Make sure that vtables for garbage collected mixin objects have

Source/platform/Supplementable.h

 /*
  * Copyright (C) 2012 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 198 matching lines @@
 private:
     ThreadIdentifier m_threadId;
 #endif
 };
 
 template<typename T>
 class HeapSupplement : public SupplementBase<T, true> { };
 
 // FIXME: Oilpan: Move GarbageCollectedMixin to SupplementableBase<T, true> once PersistentHeapSupplementable is removed again.
 template<typename T>
-class HeapSupplementable : public SupplementableBase<T, true>, public GarbageCollectedMixin { };
+class GC_PLUGIN_IGNORE("http://crbug.com/395036") HeapSupplementable : public SupplementableBase<T, true>, public GarbageCollectedMixin {

[zerny-chromium, 2014/07/19 07:21:58]

DBC this ignore is really bad since it will executively disable the plugin
checks for all derived classes too. 

[wibling-chromium, 2014/07/21 08:38:49]

FYI I am removing this ignore as part of removing off-heap tracing for hashmaps.
See
https://codereview.chromium.org/403333002/diff/1/Source/platform/Supplementab...
for details.

+public:
+    virtual void trace(Visitor* visitor) { SupplementableBase<T, true>::trace(visitor); }
+};
 
 template<typename T>
 class PersistentHeapSupplementable : public SupplementableBase<T, true> {
 public:
     PersistentHeapSupplementable() : m_root(this) { }
     virtual ~PersistentHeapSupplementable()
     {
         typedef typename SupplementableTraits<T, true>::SupplementMap::iterator SupplementIterator;
         for (SupplementIterator it = this->m_supplements.begin(); it != this->m_supplements.end(); ++it)
             it->value->persistentHostHasBeenDestroyed();
@@ skipping 22 matching lines @@
 };
 
 template<typename T>
 struct ThreadingTrait<WebCore::SupplementableBase<T, true> > {
     static const ThreadAffinity Affinity = ThreadingTrait<T>::Affinity;
 };
 
 } // namespace WebCore
 
 #endif // Supplementable_h