[ios] Use WebStateList to back the tab grid.

ios/clean/chrome/browser/ui/tab_grid/tab_grid_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.
 
 // ======                        New Architecture                         =====
 // =         This code is only used in the new iOS Chrome architecture.       =
 // ============================================================================
 
 #import "ios/clean/chrome/browser/ui/tab_grid/tab_grid_view_controller.h"
 
@@ skipping 87 matching lines @@
 
 #pragma mark - UICollectionViewDataSource methods
 
 - (NSInteger)numberOfSectionsInCollectionView:
     (UICollectionView*)collectionView {
   return 1;
 }
 
 - (NSInteger)collectionView:(UICollectionView*)collectionView
      numberOfItemsInSection:(NSInteger)section {
-  NSInteger items = [self.dataSource numberOfTabsInTabGrid];
+  int items = [self.dataSource numberOfTabsInTabGrid];
   // HACK: Do not make showing noTabsOverlay a side effect of the dataSource
   // callback.
   if (items) {
     [self removeNoTabsOverlay];
   } else {
     [self showNoTabsOverlay];
   }
   return items;
 }
 
 - (UICollectionViewCell*)collectionView:(UICollectionView*)collectionView
                  cellForItemAtIndexPath:(nonnull NSIndexPath*)indexPath {
   TabGridTabCell* cell =
       base::mac::ObjCCastStrict<TabGridTabCell>([collectionView
           dequeueReusableCellWithReuseIdentifier:[TabGridTabCell identifier]
                                     forIndexPath:indexPath]);
   cell.delegate = self;
   [cell setSessionType:TabSwitcherSessionType::REGULAR_SESSION];
-  [cell setAppearanceForTabTitle:[self.dataSource titleAtIndex:indexPath.item]
+  DCHECK_LE(indexPath.item, INT_MAX);
+  int item = static_cast<int>(indexPath.item);
+  [cell setAppearanceForTabTitle:[self.dataSource titleAtIndex:item]
                          favicon:nil
                         cellSize:CGSizeZero];
   [cell setSelected:(indexPath.item == [self.dataSource indexOfActiveTab])];
   return cell;
 }
 
 #pragma mark - UICollectionViewDelegate methods
 
 - (BOOL)collectionView:(UICollectionView*)collectionView
     shouldSelectItemAtIndexPath:(NSIndexPath*)indexPath {
@@ skipping 17 matching lines @@
   [self.settingsCommandHandler showSettings];
 }
 
 #pragma mark - TabGridActions
 
 - (void)showTabGrid:(id)sender {
   [self.tabGridCommandHandler showTabGrid];
 }
 
 - (void)createNewTab:(id)sender {
-  // PLACEHOLDER: The new WebStateList data structure will have implications
-  // on how new tabs are created.
   NSInteger index = [self.grid numberOfItemsInSection:0];
   NSIndexPath* indexPath = [NSIndexPath indexPathForItem:index inSection:0];
   auto updateBlock = ^{
     // Unselect current selected item.
-    NSInteger selectedIndex = [self.dataSource indexOfActiveTab];
     NSIndexPath* selectedIndexPath =
-        [NSIndexPath indexPathForItem:selectedIndex inSection:0];
+        [NSIndexPath indexPathForItem:[self.dataSource indexOfActiveTab]
+                            inSection:0];
     [self.grid reloadItemsAtIndexPaths:@[ selectedIndexPath ]];
 
     // Create and show new tab.
     [self.tabCommandHandler createNewTabAtIndexPath:indexPath];
     [self.tabCommandHandler showTabAtIndexPath:indexPath];
     [self.grid insertItemsAtIndexPaths:@[ indexPath ]];
   };
   [self.grid performBatchUpdates:updateBlock completion:nil];
 }
 
 #pragma mark - SessionCellDelegate
 
 - (TabSwitcherCache*)tabSwitcherCache {
   // PLACEHOLDER: return image cache.
   return nil;
 }
 
 - (void)cellPressed:(UICollectionViewCell*)cell {
-  NSInteger selectedIndex = [self.dataSource indexOfActiveTab];
+  int selectedIndex = [self.dataSource indexOfActiveTab];
   NSIndexPath* newSelectedIndexPath = [self.grid indexPathForCell:cell];
   [self.tabCommandHandler showTabAtIndexPath:newSelectedIndexPath];
-  if (newSelectedIndexPath.item != selectedIndex) {
+  if (selectedIndex == kTabGridDataSourceInvalidIndex) {
+    [self.grid reloadItemsAtIndexPaths:@[ newSelectedIndexPath ]];
+  } else if (newSelectedIndexPath.item != selectedIndex) {
     NSIndexPath* selectedIndexPath =
         [NSIndexPath indexPathForItem:selectedIndex inSection:0];
     [self.grid
         reloadItemsAtIndexPaths:@[ selectedIndexPath, newSelectedIndexPath ]];
   }
 }
 
 - (void)deleteButtonPressedForCell:(UICollectionViewCell*)cell {
   auto updateBlock = ^{
     NSIndexPath* indexPath = [self.grid indexPathForCell:cell];
@@ skipping 21 matching lines @@
   [self.grid addSubview:overlayView];
   self.noTabsOverlay = overlayView;
 }
 
 // Removes the noTabsOverlay covering the entire tab grid.
 - (void)removeNoTabsOverlay {
   [self.noTabsOverlay removeFromSuperview];
 }
 
 @end