diff --git a/Source/JavaScriptCore/runtime/Structure.h b/Source/JavaScriptCore/runtime/Structure.h
index a86a1df..8607c45 100644
--- a/Source/JavaScriptCore/runtime/Structure.h
+++ b/Source/JavaScriptCore/runtime/Structure.h
@@ -133,6 +133,7 @@
         void visitChildren(SlotVisitor&);
 
         Structure* previousID() const { ASSERT(structure()->classInfo() == &s_info); return m_previous.get(); }
+        bool transitivelyTransitionedFrom(Structure* structureToFind);
 
         void growPropertyStorageCapacity();
         unsigned propertyStorageCapacity() const { ASSERT(structure()->classInfo() == &s_info); return m_propertyStorageCapacity; }
@@ -352,6 +353,15 @@
         return Hash::Key(structure->m_nameInPrevious.get(), +structure->m_attributesInPrevious);
     }
 
+    inline bool Structure::transitivelyTransitionedFrom(Structure* structureToFind)
+    {
+        for (Structure* current = this; current; current = current->previousID()) {
+            if (current == structureToFind)
+                return true;
+        }
+        return false;
+    }
+
 } // namespace JSC
 
 #endif // Structure_h