Allow CollectionViewModel/Controller queries without SectionIdentifier

ios/chrome/browser/ui/collection_view/collection_view_controller.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/collection_view/collection_view_controller.h"
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
@@ skipping 43 matching lines @@
 }
 
 - (UIViewController*)childViewControllerForStatusBarStyle {
   return self.appBar.headerViewController;
 }
 
 - (void)loadModel {
   _collectionViewModel = [[CollectionViewModel alloc] init];
 }
 
-- (void)reconfigureCellsForItems:(NSArray*)items
-         inSectionWithIdentifier:(NSInteger)sectionIdentifier {
+- (void)reconfigureCellsForItems:(NSArray*)items {
   for (CollectionViewItem* item in items) {
-    NSIndexPath* indexPath =
-        [self.collectionViewModel indexPathForItem:item
-                           inSectionWithIdentifier:sectionIdentifier];
+    NSIndexPath* indexPath = [self.collectionViewModel indexPathForItem:item];
     [self reconfigureCellAtIndexPath:indexPath withItem:item];
   }
 }
 
 - (void)reconfigureCellsAtIndexPaths:(NSArray*)indexPaths {
   for (NSIndexPath* indexPath in indexPaths) {
     CollectionViewItem* item =
         [self.collectionViewModel itemAtIndexPath:indexPath];
     [self reconfigureCellAtIndexPath:indexPath withItem:item];
   }
@@ skipping 197 matching lines @@
       base::mac::ObjCCastStrict<MDCCollectionViewCell>(
           [self.collectionView cellForItemAtIndexPath:indexPath]);
 
   // |cell| may be nil if the row is not currently on screen.
   if (cell) {
     [item configureCell:cell];
   }
 }
 
 @end