Add a message to empty ContentSuggestions sections

ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm

Index: ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm
diff --git a/ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm b/ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm
index 4447d4ad793506e02321ee92df81ab1afe255477..bea4610b3f01378aee9f95451d9c242bc4274d53 100644
--- a/ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm
+++ b/ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm
@@ -65,6 +65,9 @@ const NSTimeInterval kAnimationDuration = 0.35;
         willDeleteItemsAtIndexPaths:@[ indexPath ]];
 
     [self.collectionView deleteItemsAtIndexPaths:@[ indexPath ]];
+
+    // Check if the section is now empty.
+    [self addEmptySectionPlaceholderIfNeeded:indexPath.section];
   }
       completion:^(BOOL) {
         // The context menu could be displayed for the deleted entry.
@@ -140,6 +143,8 @@ const NSTimeInterval kAnimationDuration = 0.35;
     case ContentSuggestionTypeArticle:
       [self openArticle:item];
       break;
+    case ContentSuggestionTypeEmpty:
+      break;
   }
 }
 
@@ -267,4 +272,15 @@ const NSTimeInterval kAnimationDuration = 0.35;
                        atIndexPath:touchedItemIndexPath];
 }
 
+// Checks if the |section| is empty and add an empty element if it is the case.
+// Must be called from inside a performBatchUpdates: block.
+- (void)addEmptySectionPlaceholderIfNeeded:(NSInteger)section {
+  if ([self.collectionViewModel numberOfItemsInSection:section] > 0)
+    return;
+
+  NSIndexPath* emptyItem =
+      [self.collectionUpdater addEmptyItemForSection:section];
+  [self.collectionView insertItemsAtIndexPaths:@[ emptyItem ]];
+}
+
 @end