Oilpan: Ensure that classes with virtual trace methods always have vtables for their left-most base…

Source/platform/Supplementable.h

Index: Source/platform/Supplementable.h
diff --git a/Source/platform/Supplementable.h b/Source/platform/Supplementable.h
index 650a204bd57cbbee12b7ebf1ad25f73e6e3b5791..2d517397f17eaf39ea6aedc48257e583a5cd88f0 100644
--- a/Source/platform/Supplementable.h
+++ b/Source/platform/Supplementable.h
@@ -154,7 +154,14 @@ template<typename T, bool>
 class SupplementableTracing;
 
 template<typename T>
-class SupplementableTracing<T, true> { };
+class SupplementableTracing<T, true> {
+public:
+    // We have a trace method in SupplementableTracing<T, true> to ensure we have
+    // the vtable at the first word of the object. However we don't trace the
+    // m_supplements here, but in the partially specialized template subclasses
+    // since we only want to trace it for garbage collected classes.
+    virtual void trace(Visitor*) { }
+};
 
 template<typename T>
 class SupplementableTracing<T, false> { };
@@ -190,12 +197,6 @@ public:
 #endif
     }
 
-    // We have a trace method in the SupplementableBase class to ensure we have
-    // the vtable at the first word of the object. However we don't trace the
-    // m_supplements here, but in the partially specialized template subclasses
-    // since we only want to trace it for garbage collected classes.
-    virtual void trace(Visitor*) { }
-
     void willBeDestroyed()
     {
         typedef typename SupplementableTraits<T, isGarbageCollected>::SupplementMap::iterator SupplementIterator;