Oilpan: support eager tracing of objects when marking.

Source/platform/heap/HeapLinkedStack.h

Index: Source/platform/heap/HeapLinkedStack.h
diff --git a/Source/platform/heap/HeapLinkedStack.h b/Source/platform/heap/HeapLinkedStack.h
index 2ad0bb206ce3498376003cf45e1d4e2844e86f9d..e7d776512f12184f900073191947f5b61b0a39db 100644
--- a/Source/platform/heap/HeapLinkedStack.h
+++ b/Source/platform/heap/HeapLinkedStack.h
@@ -56,7 +56,7 @@ public:
     }
 
 private:
-    class Node : public GarbageCollected<Node> {
+    class Node : public GarbageCollected<Node>, public TraceEagerly {
     public:
         Node(const T&, Node* next);
 
@@ -110,6 +110,12 @@ inline size_t HeapLinkedStack<T>::size()
     return m_size;
 }
 
-}
+template<typename T>
+class TraceEagerlyTrait<HeapLinkedStack<T> > {
+public:
+    static const bool value = IS_EAGERLY_TRACED_HEAP_COLLECTION(T);
+};
+
+} // namespace blink
 
 #endif // HeapLinkedStack_h