inner_class.cpp:9:1: warning: [blink-gc] Class 'InnerObject' has untraced fields that require tracing. void SomeObject::InnerObject::Trace(Visitor* visitor) ^ ./inner_class.h:18:9: note: [blink-gc] Untraced field 'm_obj' declared here: Member<InnerObject> m_obj; ^ 1 warning generated.