[ios] Plumb SnapshotCache into tab grid.

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 10 matching lines @@
 // The model backing the collection view.
 @property(nonatomic, readwrite) NSMutableArray<TabCollectionItem*>* items;
 // Selected index of tab collection.
 @property(nonatomic, assign) int selectedIndex;
 @end
 
 @implementation TabCollectionViewController
 @synthesize tabs = _tabs;
 @synthesize items = _items;
 @synthesize selectedIndex = _selectedIndex;
+@synthesize snapshotCache = _snapshotCache;
 
 #pragma mark - UIViewController
 
 - (void)viewDidLoad {
   [super viewDidLoad];
   UICollectionView* tabs =
       [[UICollectionView alloc] initWithFrame:CGRectZero
                          collectionViewLayout:[self collectionViewLayout]];
   tabs.translatesAutoresizingMaskIntoConstraints = NO;
   tabs.backgroundColor = [UIColor blackColor];
@@ skipping 70 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);
-  // PLACEHOLDER: SnapshotCache will be passed into the cell.
-  [cell configureCell:self.items[index] snapshotCache:nil];
+  [cell configureCell:self.items[index] snapshotCache:self.snapshotCache];
   return cell;
 }
 
 #pragma mark - UICollectionViewDelegate methods
 
 - (BOOL)collectionView:(UICollectionView*)collectionView
     shouldSelectItemAtIndexPath:(NSIndexPath*)indexPath {
   // Prevent user selection of items.
   return NO;
 }
@@ skipping 54 matching lines @@
 }
 
 - (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]]);
-  // PLACEHOLDER: SnapshotCache will be passed into the cell.
-  [cell configureCell:self.items[index] snapshotCache:nil];
+  [cell configureCell:self.items[index] snapshotCache:self.snapshotCache];
 }
 
 - (void)populateItems:(NSArray<TabCollectionItem*>*)items
         selectedIndex:(int)selectedIndex {
   self.items = [items mutableCopy];
   [self.tabs reloadItemsAtIndexPaths:[self.tabs indexPathsForVisibleItems]];
   self.selectedIndex = selectedIndex;
 }
 
 @end