Add a way to reconfigure cell from IndexPaths

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

Index: ios/chrome/browser/ui/collection_view/collection_view_controller.mm
diff --git a/ios/chrome/browser/ui/collection_view/collection_view_controller.mm b/ios/chrome/browser/ui/collection_view/collection_view_controller.mm
index 3914205819c4c2e2e8292078ee5f2d8bd9978e74..050eb0ee2a206aac102d4cc3afb2096b5fcac132 100644
--- a/ios/chrome/browser/ui/collection_view/collection_view_controller.mm
+++ b/ios/chrome/browser/ui/collection_view/collection_view_controller.mm
@@ -74,14 +74,15 @@
     NSIndexPath* indexPath =
         [self.collectionViewModel indexPathForItem:item
                            inSectionWithIdentifier:sectionIdentifier];
-    MDCCollectionViewCell* cell =
-        base::mac::ObjCCastStrict<MDCCollectionViewCell>(
-            [self.collectionView cellForItemAtIndexPath:indexPath]);
+    [self reconfigureCellAtIndexPath:indexPath withItem:item];
+  }
+}
 
-    // |cell| may be nil if the row is not currently on screen.
-    if (cell) {
-      [item configureCell:cell];
-    }
+- (void)reconfigureCellsAtIndexPaths:(NSArray*)indexPaths {
+  for (NSIndexPath* indexPath in indexPaths) {
+    CollectionViewItem* item =
+        [self.collectionViewModel itemAtIndexPath:indexPath];
+    [self reconfigureCellAtIndexPath:indexPath withItem:item];
   }
 }
 
@@ -268,4 +269,19 @@
   }
 }
 
+#pragma mark - Private
+
+// Reconfigures the cell at |indexPath| by calling |configureCell:| with |item|.
+- (void)reconfigureCellAtIndexPath:(NSIndexPath*)indexPath
+                          withItem:(CollectionViewItem*)item {
+  MDCCollectionViewCell* cell =
+      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