Update the edit button when all entries are gone.

Bug: 719940
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I3f4ca925dd4e4378e5f7ae8fcb5276660a9cb5fc
Reviewed-on: https://chromium-review.googlesource.com/776816
Commit-Queue: Louis Romero <lpromero@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517801}

ios/chrome/browser/ui/settings/block_popups_collection_view_controller.mm

@@ -180,6 +180,9 @@ typedef NS_ENUM(NSInteger, ItemType) {
     _exceptions.Remove(urlIndex, NULL);
   }
 
+  // Update the edit button appearance, in case all exceptions were removed.
+  [self updateEditButton];
+
   // Must call super at the end of the child implementation.
   [super collectionView:collectionView willDeleteItemsAtIndexPaths:indexPaths];
 }