WTF::notFound looks too much like a local variable.

Source/core/tests/ArenaTestHelpers.h

Index: Source/core/tests/ArenaTestHelpers.h
diff --git a/Source/core/tests/ArenaTestHelpers.h b/Source/core/tests/ArenaTestHelpers.h
index 0e60ca590ac2a6465dabfd80d9eba06ba6ce6426..dd94743f30aac100717416be1b78dfb2f5cfa975 100644
--- a/Source/core/tests/ArenaTestHelpers.h
+++ b/Source/core/tests/ArenaTestHelpers.h
@@ -54,7 +54,7 @@ public:
     virtual void free(void* ptr)
     {
         size_t slot = m_allocatedRegions.find(ptr);
-        ASSERT_NE(slot, notFound);
+        ASSERT_NE(slot, kNotFound);
         m_allocatedRegions.remove(slot);
         PODArena::FastMallocAllocator::free(ptr);
     }