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

Source/platform/Supplementable.h

Index: Source/platform/Supplementable.h
diff --git a/Source/platform/Supplementable.h b/Source/platform/Supplementable.h
index eac9f5e9f8adae336a47a7e2f7c0b2873230f00d..2ff505009b98554a529db17c6cceda99b37eac1b 100644
--- a/Source/platform/Supplementable.h
+++ b/Source/platform/Supplementable.h
@@ -216,7 +216,10 @@ 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> {