Allow CollectionViewModel/Controller queries without SectionIdentifier

ios/chrome/browser/ui/collection_view/collection_view_model.mm

Index: ios/chrome/browser/ui/collection_view/collection_view_model.mm
diff --git a/ios/chrome/browser/ui/collection_view/collection_view_model.mm b/ios/chrome/browser/ui/collection_view/collection_view_model.mm
index 0866b37bdafde7636ef71ab9c88f608417224f14..460091ffc9a7435bbbc74e89834abac1689c72fa 100644
--- a/ios/chrome/browser/ui/collection_view/collection_view_model.mm
+++ b/ios/chrome/browser/ui/collection_view/collection_view_model.mm
@@ -267,6 +267,25 @@ typedef NSMutableArray<CollectionViewItem*> SectionItems;
   return [NSIndexPath indexPathForItem:itemIndex inSection:section];
 }
 
+- (BOOL)hasItem:(CollectionViewItem*)item {
+  for (SectionItems* sectionItems in _sections) {
+    if ([sectionItems indexOfObject:item] != NSNotFound)
+      return YES;
+  }
+  return NO;
+}
+
+- (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];
+    }
+  }
+  DCHECK(NO);

[lpromero, 2017/03/22 14:04:22]

Use NOTREACHED.

+  return nil;
+}
+
 #pragma mark UICollectionView data sourcing
 
 - (NSInteger)numberOfSections {