1persistent_no_trace.cpp:9:1: warning: [blink-gc] Class 'HeapObject' has untraced or not traceable fields. 2void HeapObject::trace(Visitor* visitor) { 3^ 4./persistent_no_trace.h:16:5: note: [blink-gc] Untraceable field 'm_crossThreadPersistent' declared here: 5 CrossThreadPersistent<HeapObject> m_crossThreadPersistent; 6 ^ 7./persistent_no_trace.h:17:5: note: [blink-gc] Untraceable field 'm_crossThreadWeakPersistent' declared here: 8 CrossThreadWeakPersistent<HeapObject> m_crossThreadWeakPersistent; 9 ^ 101 warning generated. 11