Allow CollectionViewModel/Controller queries without SectionIdentifier

ios/chrome/browser/ui/collection_view/collection_view_controller.h

 // 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.
 
 #ifndef IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_COLLECTION_VIEW_CONTROLLER_H_
 #define IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_COLLECTION_VIEW_CONTROLLER_H_
 
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 #import "ios/chrome/browser/ui/material_components/app_bar_presenting.h"
 #import "ios/third_party/material_components_ios/src/components/Collections/src/MaterialCollections.h"
@@ skipping 29 matching lines @@
 
 // Initializes the collection view model. Must be called by subclasses if they
 // override this method in order to get a clean collectionViewModel.
 - (void)loadModel NS_REQUIRES_SUPER;
 
 // Reconfigures the cells corresponding to the given |items| by calling
 // |configureCell:| on each cell.
 - (void)reconfigureCellsForItems:(NSArray*)items
          inSectionWithIdentifier:(NSInteger)sectionIdentifier;
 
+// Reconfigures the cells corresponding to the given |items| by calling
+// |configureCell:| on each cell.
+- (void)reconfigureCellsForItems:(NSArray*)items;
+
 // Reconfigures the cells corresponding to the given |indexPaths| by calling
 // |configureCell:| on each cell.
 - (void)reconfigureCellsAtIndexPaths:(NSArray*)indexPaths;
 
 #pragma mark MDCCollectionViewEditingDelegate
 
 // Updates the model with changes to the collection view items. Must be called
 // by subclasses if they override this method in order to maintain this
 // functionality.
 - (void)collectionView:(UICollectionView*)collectionView
@@ skipping 29 matching lines @@
 // state. Must be called by subclasses if they override this method in order to
 // maintain this functionality.
 - (void)scrollViewWillEndDragging:(UIScrollView*)scrollView
                      withVelocity:(CGPoint)velocity
               targetContentOffset:(inout CGPoint*)targetContentOffset
     NS_REQUIRES_SUPER;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_COLLECTION_VIEW_CONTROLLER_H_