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 238 matching lines @@
 }
 
 #pragma mark Query index paths from items
 
 - (BOOL)hasItem:(CollectionViewItem*)item
     inSectionWithIdentifier:(NSInteger)sectionIdentifier {
   return [[self itemsInSectionWithIdentifier:sectionIdentifier]
              indexOfObject:item] != NSNotFound;
 }
 
-- (NSIndexPath*)indexPathForItem:(CollectionViewItem*)item
-         inSectionWithIdentifier:(NSInteger)sectionIdentifier {
-  NSArray* itemsInSection =
-      [self itemsInSectionWithIdentifier:sectionIdentifier];
+- (BOOL)hasItem:(CollectionViewItem*)item {
+  for (NSNumber* section in _sectionIdentifiers) {
+    if ([self hasItem:item inSectionWithIdentifier:[section integerValue]])
+      return YES;
+  }
+  return NO;
+}
 
-  NSInteger section = [self sectionForSectionIdentifier:sectionIdentifier];
-  NSInteger itemIndex = [itemsInSection indexOfObject:item];
-  DCHECK_NE(NSNotFound, itemIndex);
-  return [NSIndexPath indexPathForItem:itemIndex inSection:section];
+- (NSIndexPath*)indexPathForItem:(CollectionViewItem*)item {
+  for (NSUInteger section = 0; section < _sections.count; section++) {
+    NSInteger itemIndex = [_sections[section] indexOfObject:item];
+    if (itemIndex != NSNotFound) {
+      return [NSIndexPath indexPathForItem:itemIndex inSection:section];
+    }
+  }
+  NOTREACHED();
+  return nil;
 }
 
 #pragma mark UICollectionView data sourcing
 
 - (NSInteger)numberOfSections {
   return [_sections count];
 }
 
 - (NSInteger)numberOfItemsInSection:(NSInteger)section {
   DCHECK_LT(static_cast<NSUInteger>(section), [_sections count]);
@@ skipping 44 matching lines @@
     }
     if (sectionItem.type == item.type) {
       indexInItemType++;
     }
   }
   DCHECK(found);
   return indexInItemType;
 }
 
 @end