[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 tabs = [self.dataSource numberOfTabsInTabGrid];
+  DCHECK_LE(tabs, NSIntegerMax);

[sdefresne, 2017/03/14 09:04:08]

This is unnecessary, NSInteger is at least as large as int.

From Objective-C documentation:
  > When building 32-bit applications, NSInteger is a 32-bit integer.
  > A 64-bit application treats NSInteger as a 64-bit integer.

NSInteger is in fact a typedef for long, and the C (and C++) standard guarantees
that long is at least as large as int (in fact, it order types in char, short,
int, long, long long and guarantees that each is at least as large as the
previous one and only gives lower bound on the type size).

TL;DR: remove the DCHECK and cast here.

[edchin, 2017/03/14 16:02:42]

Done.

+  NSInteger items = static_cast<NSInteger>(tabs);
   // 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])];
+  int tab = [self.dataSource indexOfActiveTab];
+  DCHECK_LE(tab, NSIntegerMax);

[sdefresne, 2017/03/14 09:04:08]

ditto, remove the DCHECK and cast here (int -> NSInteger is safe)

+  NSInteger index = static_cast<NSInteger>(tab);
+  [cell setSelected:(indexPath.item == index)];
   return cell;
 }
 
 #pragma mark - UICollectionViewDelegate methods
 
 - (BOOL)collectionView:(UICollectionView*)collectionView
     shouldSelectItemAtIndexPath:(NSIndexPath*)indexPath {
   // Prevent user selection of items.
   return NO;
 }
@@ skipping 14 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];
+    int index = [self.dataSource indexOfActiveTab];
+    DCHECK_LE(index, NSIntegerMax);

[sdefresne, 2017/03/14 09:04:08]

ditto, remove the DCHECK and cast here (int -> NSInteger is safe)

+    NSInteger selectedIndex = static_cast<NSInteger>(index);
     NSIndexPath* selectedIndexPath =
         [NSIndexPath indexPathForItem:selectedIndex 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 index = [self.dataSource indexOfActiveTab];
+  DCHECK_LE(index, NSIntegerMax);

[sdefresne, 2017/03/14 09:04:09]

ditto, remove the DCHECK and cast here (int -> NSInteger is safe)

+  NSInteger selectedIndex = static_cast<NSInteger>(index);
   NSIndexPath* newSelectedIndexPath = [self.grid indexPathForCell:cell];
   [self.tabCommandHandler showTabAtIndexPath:newSelectedIndexPath];
   if (newSelectedIndexPath.item != selectedIndex) {
     NSIndexPath* selectedIndexPath =
         [NSIndexPath indexPathForItem:selectedIndex inSection:0];
     [self.grid
         reloadItemsAtIndexPaths:@[ selectedIndexPath, newSelectedIndexPath ]];
   }
 }
 
@@ skipping 24 matching lines @@
   [self.grid addSubview:overlayView];
   self.noTabsOverlay = overlayView;
 }
 
 // Removes the noTabsOverlay covering the entire tab grid.
 - (void)removeNoTabsOverlay {
   [self.noTabsOverlay removeFromSuperview];
 }
 
 @end