[Oilpan] Add use-after-free detector in Member<>

third_party/WebKit/Source/platform/heap/GarbageCollected.h

Index: third_party/WebKit/Source/platform/heap/GarbageCollected.h
diff --git a/third_party/WebKit/Source/platform/heap/GarbageCollected.h b/third_party/WebKit/Source/platform/heap/GarbageCollected.h
index d9abbd3a2af03f801b57b211bcde0a65a25b1231..5559fc27cdbbea7192b9d8bca46291e2c4b5a17e 100644
--- a/third_party/WebKit/Source/platform/heap/GarbageCollected.h
+++ b/third_party/WebKit/Source/platform/heap/GarbageCollected.h
@@ -128,6 +128,7 @@ public:
     virtual void adjustAndMark(InlinedGlobalMarkingVisitor) const = 0;
     virtual void trace(InlinedGlobalMarkingVisitor);
     virtual bool isHeapObjectAlive() const = 0;
+    virtual HeapObjectHeader* heapObjectHeader() const = 0;
 };
 
 #define DEFINE_GARBAGE_COLLECTED_MIXIN_METHODS(VISITOR, TYPE)           \
@@ -205,6 +206,10 @@ public:                                                                 \
     {                                                                   \
         return Heap::isHeapObjectAlive(this);                           \
     }                                                                   \
+    HeapObjectHeader* heapObjectHeader() const override                 \
+    {                                                                   \
+        return HeapObjectHeader::fromPayload(this);                     \
+    }                                                                   \
 private:
 
 #if ENABLE(OILPAN)