Though a grant be not actually delivered into the possession of the grantee, it is yet to be deemed constructively delivered in the following cases:

1. Where the instrument is, by the agreement of the parties at the time of execution, understood to be delivered, and under such circumstances that the grantee is entitled to immediate delivery; or,

2. Where it is delivered to a stranger for the benefit of the grantee, and his assent is shown, or may be presumed.