title: Core Data viewContext not receiving updates from newBackgroundContext() with NSFetchedResultsController
body: <p>In my application, I have a <code>NSFetchedResultsController</code> to load Core Data objects in a UITableView.
  The fetch request associated with this FRC uses the new <code>viewContext</code> property available for the <code>NSPersistentContainer</code> (iOS10).</p>
  
  <p>When I select a cell, I pass the Core Data object to a new ViewController. This new VC still uses the viewContext.
  From this ViewController, I can update the Core Data object from ViewControllers presented modally. To do so, I use <code>newBackgroundContext()</code> for the modal ViewControllers. I can save the update Core Data object without any issue.</p>
  
  <p>The problem is that the FRC is not automatically updated with the update Core Data object from the background context.
  It is as if the viewContext was not receivng and handling the Core Data object updates.</p>
  
  <p>If I set <code>automaticallyMergesChangesFromParent</code> to true for the viewContext (app wide), the FRC gets the updated Core Data object when I save the background context. From my understanding, the viewContext should manage the merge of data automatically. The documentation describes the viewContext with: <em>"This context is configured to be generational and to automatically consume save notifications from other contexts."</em></p>
  
  <p>Can you clarify how to handle the different contexts with a NSFetchedResultsController?</p>