[ios] TabCollectionTabCell to use SnapshotCache.

ios/clean/chrome/browser/ui/tab_collection/tab_collection_view_controller.mm

 // Copyright 2017 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/clean/chrome/browser/ui/tab_collection/tab_collection_view_controller.h"
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 #import "ios/clean/chrome/browser/ui/tab_collection/tab_collection_item.h"
@@ skipping 100 matching lines @@
                  cellForItemAtIndexPath:(nonnull NSIndexPath*)indexPath {
   TabCollectionTabCell* cell =
       base::mac::ObjCCastStrict<TabCollectionTabCell>([collectionView
           dequeueReusableCellWithReuseIdentifier:[TabCollectionTabCell
                                                      identifier]
                                     forIndexPath:indexPath]);
   cell.delegate = self;
   [cell setSessionType:TabSwitcherSessionType::REGULAR_SESSION];
   DCHECK_LE(indexPath.item, INT_MAX);
   int index = static_cast<int>(indexPath.item);
-  cell.item = self.items[index];
+  // PLACEHOLDER: SnapshotCache will be passed into the cell.
+  [cell configureCell:self.items[index] snapshotCache:nil];
   return cell;
 }
 
 #pragma mark - UICollectionViewDelegate methods
 
 - (BOOL)collectionView:(UICollectionView*)collectionView
     shouldSelectItemAtIndexPath:(NSIndexPath*)indexPath {
   // Prevent user selection of items.
   return NO;
 }
 
 #pragma mark - SessionCellDelegate
 
 - (TabSwitcherCache*)tabSwitcherCache {
-  // PLACEHOLDER: return image cache.
+  // PLACEHOLDER: SnapshotCache will be passed into the cell.
   return nil;
 }
 
 - (void)cellPressed:(UICollectionViewCell*)cell {
   NSInteger item = [[self.tabs indexPathForCell:cell] item];
   DCHECK_LE(item, INT_MAX);
   int index = static_cast<int>(item);
   [self showTabAtIndex:index];
 }
 
@@ skipping 32 matching lines @@
   TabCollectionItem* item = self.items[fromIndex];
   [self.items removeObjectAtIndex:fromIndex];
   [self.items insertObject:item atIndex:toIndex];
   [self.tabs
       moveItemAtIndexPath:[NSIndexPath indexPathForItem:fromIndex inSection:0]
               toIndexPath:[NSIndexPath indexPathForItem:toIndex inSection:0]];
   self.selectedIndex = selectedIndex;
 }
 
 - (void)replaceItemAtIndex:(int)index withItem:(TabCollectionItem*)item {
+  DCHECK(item);
   DCHECK_GE(index, 0);
   DCHECK_LT(static_cast<NSUInteger>(index), self.items.count);
   self.items[index] = item;
   TabCollectionTabCell* cell = base::mac::ObjCCastStrict<TabCollectionTabCell>(
       [self.tabs cellForItemAtIndexPath:[NSIndexPath indexPathForItem:index
                                                             inSection:0]]);
-  cell.item = self.items[index];
+  // PLACEHOLDER: SnapshotCache will be passed into the cell.
+  [cell configureCell:self.items[index] snapshotCache:nil];
 }
 
 - (void)populateItems:(NSArray<TabCollectionItem*>*)items
         selectedIndex:(int)selectedIndex {
   self.items = [items mutableCopy];
   [self.tabs reloadItemsAtIndexPaths:[self.tabs indexPathsForVisibleItems]];
   self.selectedIndex = selectedIndex;
 }
 
 @end