For the purposes of this chapter, “beneficiary of the decedent’s estate” means:
(a) If the decedent died leaving a will, the sole beneficiary or all of the beneficiaries who succeed to a cause of action, or to a particular item of property that is the subject of a cause of action, under the decedent’s will.
(b) If the decedent died without leaving a will, the sole person or all of the persons who succeed to a cause of action, or to a particular item of property that is the subject of a cause of action, under Sections 6401 and 6402 of the Probate Code or, if the law of a sister state or foreign nation governs succession to the cause of action or particular item of property, under the law of the sister state or foreign nation.