Fix section reload in NTP

When a ContentSuggestions section is reloaded in the NTP, it is possible
that new sections/items in other sections are added.
This CL makes sure that the collection is updated to take those new
elements into account.

Bug: 866849
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Id474ca33afdafb18871b2bb77e4a94e8bfe1cc68
Reviewed-on: https://chromium-review.googlesource.com/1154986
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579416}

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

@@ -336,9 +336,6 @@ NSString* const kContentSuggestionsCollectionUpdaterSnackbarCategory =
   for (NSInteger i = 0; i < numberOfItems; i++) {
     [oldItems addObject:[NSIndexPath indexPathForItem:i inSection:section]];
   }
-  [self.collectionViewController
-                   collectionView:self.collectionViewController.collectionView
-      willDeleteItemsAtIndexPaths:oldItems];
 
   // Reset collection model data for |sectionIdentifier|
   [self.collectionViewController.collectionViewModel
@@ -349,11 +346,30 @@ NSString* const kContentSuggestionsCollectionUpdaterSnackbarCategory =
       forSectionWithIdentifier:sectionIdentifier];
   [self.sectionIdentifiersFromContentSuggestions
       removeObject:@(sectionIdentifier)];
-  [self.collectionViewController.collectionViewModel
-      removeSectionWithIdentifier:sectionIdentifier];
-  [self addSectionsForSectionInfoToModel:@[ sectionInfo ]];
-  [self addSuggestionsToModel:[self.dataSource itemsForSectionInfo:sectionInfo]
+
+  // Update the section and the other ones.
+  auto addSectionBlock = ^{
+    [self.collectionViewController.collectionViewModel
+        removeSectionWithIdentifier:sectionIdentifier];
+    [self.collectionViewController.collectionView
+        deleteSections:[NSIndexSet indexSetWithIndex:section]];
+
+    NSIndexSet* addedSections =
+        [self addSectionsForSectionInfoToModel:@[ sectionInfo ]];
+    [self.collectionViewController.collectionView insertSections:addedSections];
+
+    NSArray<NSIndexPath*>* addedItems = [self
+        addSuggestionsToModel:[self.dataSource itemsForSectionInfo:sectionInfo]
               withSectionInfo:sectionInfo];
+    [self.collectionViewController.collectionView
+        insertItemsAtIndexPaths:addedItems];
+  };
+  [self.collectionViewController.collectionView
+      performBatchUpdates:addSectionBlock
+               completion:nil];
+
+  // Make sure we get the right index for the section.
+  section = [model sectionForSectionIdentifier:sectionIdentifier];
 
   [self.collectionViewController.collectionView
       reloadSections:[NSIndexSet indexSetWithIndex:section]];

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

@@ -794,8 +794,10 @@ GREYElementInteraction* CellWithMatcher(id<GREYMatcher> matcher) {
 
   // Check the tile is back.
   [[EarlGrey selectElementWithMatcher:
-                 chrome_test_util::StaticTextWithAccessibilityLabel(pageTitle)]
-      assertWithMatcher:grey_sufficientlyVisible()];
+                 grey_allOf(chrome_test_util::StaticTextWithAccessibilityLabel(
+                                pageTitle),
+                            grey_sufficientlyVisible(), nil)]
+      assertWithMatcher:grey_notNil()];
 }
 
 // Tests that the context menu has the correct actions.