You have rented, by agreement with Google, a portion of the space on their servers. It's no different than a physical storage locker at a storage facility. Yes,

You have rented, by agreement with Google, a portion of the space on their servers. It's no different than a physical storage locker at a storage facility. Yes, that is property that is owned by a third party, but you've still entered into an agreement for the exclusive use of it and you have an expectation of privacy. Police are not allowed to search it without a warrant.