The object that is managing semantics for this pipeline owner, if any.
An owner is created by ensureSemantics. The owner is valid for as long there are SemanticsHandle returned by ensureSemantics that have not yet be disposed. Once the last handle has been disposed, the semanticsOwner field will revert to null, and the previous owner will be disposed.
When semanticsOwner is null, the PipelineOwner skips all steps relating to semantics.
Source
SemanticsOwner get semanticsOwner => _semanticsOwner;