Reload the Most Visited section when it changes

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.h"
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/time/time.h"
@@ skipping 203 matching lines @@
 
 - (void)clearSection:(ContentSuggestionsSectionInformation*)sectionInfo {
   SectionIdentifier sectionIdentifier = SectionIdentifierForInfo(sectionInfo);
   NSInteger section = [self.collectionViewController.collectionViewModel
       sectionIdentifierForSection:sectionIdentifier];
 
   [self.collectionViewController dismissSection:section];
 }
 
 - (void)reloadSection:(ContentSuggestionsSectionInformation*)sectionInfo {
-  // TODO(crbug.com/707754): implement this method.
+  CSCollectionViewModel* model =
+      self.collectionViewController.collectionViewModel;
+  SectionIdentifier sectionIdentifier = SectionIdentifierForInfo(sectionInfo);
+
+  if (![model hasSectionForSectionIdentifier:sectionIdentifier]) {
+    [self.collectionViewController
+        addSuggestions:[self.dataSource itemsForSectionInfo:sectionInfo]
+         toSectionInfo:sectionInfo];
+    return;
+  }
+
+  NSInteger section = [model sectionForSectionIdentifier:sectionIdentifier];
+
+  NSMutableArray* oldItems = [NSMutableArray array];
+  NSInteger numberOfItems = [model numberOfItemsInSection:section];
+  for (NSInteger i = 0; i < numberOfItems; i++) {
+    [oldItems addObject:[NSIndexPath indexPathForItem:i inSection:section]];
+  }
+  [self.collectionViewController
+                   collectionView:self.collectionViewController.collectionView
+      willDeleteItemsAtIndexPaths:oldItems];
+
+  [self addSuggestionsToModel:[self.dataSource itemsForSectionInfo:sectionInfo]
+              withSectionInfo:sectionInfo];
+
+  [self.collectionViewController.collectionView
+      reloadSections:[NSIndexSet indexSetWithIndex:section]];
 }
 
 - (void)faviconAvailableForItem:(CollectionViewItem<SuggestedContent>*)item {
   if ([self.collectionViewController.collectionViewModel hasItem:item]) {
     [self fetchFaviconForItem:item];
   }
 }
 
 #pragma mark - Public methods
 
@@ skipping 354 matching lines @@
 }
 
 // Returns the maximum number of Most Visited tiles to be displayed in the
 // collection.
 - (NSInteger)mostVisitedPlaceCount {
   return content_suggestions::numberOfTilesForWidth(self.collectionWidth) *
          kNumberOfMostVisitedLines;
 }
 
 @end