Allow CollectionViewModel/Controller queries without SectionIdentifier

ios/chrome/browser/ui/collection_view/collection_view_model.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.
 
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 
 #include "base/logging.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
@@ skipping 249 matching lines @@
          inSectionWithIdentifier:(NSInteger)sectionIdentifier {
   NSArray* itemsInSection =
       [self itemsInSectionWithIdentifier:sectionIdentifier];
 
   NSInteger section = [self sectionForSectionIdentifier:sectionIdentifier];
   NSInteger itemIndex = [itemsInSection indexOfObject:item];
   DCHECK_NE(NSNotFound, itemIndex);
   return [NSIndexPath indexPathForItem:itemIndex inSection:section];
 }
 
+- (BOOL)hasItem:(CollectionViewItem*)item {
+  for (SectionItems* sectionItems in _sections) {

[lpromero, 2017/03/28 09:09:08]

Iterate on _sectionIdentifiers and use haseItem:inSectionWithIdentifier:.

[gambard, 2017/03/28 13:35:22]

I wanted to offer a solution without the current implementation in case we
wanted to remove the current implementation.
Done.

+    if ([sectionItems indexOfObject:item] != NSNotFound)
+      return YES;
+  }
+  return NO;
+}
+
+- (NSIndexPath*)indexPathForItem:(CollectionViewItem*)item {
+  for (NSUInteger section = 0; section < [_sections count]; section++) {

[lpromero, 2017/03/28 09:09:08]

Idem, use the same methods that use the sectionIdentifier.

[gambard, 2017/03/28 13:35:22]

This method was slightly more efficient (lookup only once in the section
containing the item).
Done anyway.

+    NSInteger itemIndex = [_sections[section] indexOfObject:item];
+    if (itemIndex != NSNotFound) {
+      return [NSIndexPath indexPathForItem:itemIndex inSection:section];
+    }
+  }
+  DCHECK(NO);

[lpromero, 2017/03/28 09:09:08]

Use NOTREACHED().

[gambard, 2017/03/28 13:35:22]

Done.

+  return nil;
+}
+
 #pragma mark UICollectionView data sourcing
 
 - (NSInteger)numberOfSections {
   return [_sections count];
 }
 
 - (NSInteger)numberOfItemsInSection:(NSInteger)section {
   DCHECK_LT(static_cast<NSUInteger>(section), [_sections count]);
   SectionItems* items = [_sections objectAtIndex:section];
   return items.count;
@@ skipping 42 matching lines @@
     }
     if (sectionItem.type == item.type) {
       indexInItemType++;
     }
   }
   DCHECK(found);
   return indexInItemType;
 }
 
 @end