The ContentEntityStorageBase abstract class defines a set of new abstract methods responsible for encapsulating the logic dealing with raw storage read/writes.
The ::doSaveFieldItems() method that should encapsulate all the logic to perform a raw write of field item values to the storage. The method has an optional $names parameter, which will hold the names of the field items to be written to the storage. This parameter is empty by default, in which case a full entity save workflow should be assumed. If the names array is not empty only the related item values should be written to the storage and no assumption should be made on the current workflow. For an example, see SqlContentEntityStorage::doSaveFieldItems().
Other abstract methods added are:
::doDeleteFieldItems()::doDeleteRevisionFieldItems()::doLoadRevisionFieldItems()
