Allow CollectionViewModel/Controller queries without SectionIdentifier

ios/chrome/browser/ui/collection_view/collection_view_model_unittest.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/bind.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/strings/string_piece.h"
@@ skipping 504 matching lines @@
   [model addItemWithType:ItemTypeWeasleyArthur
       toSectionWithIdentifier:SectionIdentifierWeasley];
   // Repeated item added at index 4.
   CollectionViewItem* item4 =
       [[CollectionViewItem alloc] initWithType:ItemTypeWeasleyArthur];
   [model addItem:item4 toSectionWithIdentifier:SectionIdentifierWeasley];
   [model addItemWithType:ItemTypeWeasleyArthur
       toSectionWithIdentifier:SectionIdentifierWeasley];
   [model addItemWithType:ItemTypeWeasleyArthur
       toSectionWithIdentifier:SectionIdentifierWeasley];
+  // Item not added.
+  CollectionViewItem* notAddedItem =
+      [[CollectionViewItem alloc] initWithType:ItemTypeCheeseGouda];
 
-  NSIndexPath* indexPath1 = [model indexPathForItem:item1
-                            inSectionWithIdentifier:SectionIdentifierWeasley];
+  EXPECT_TRUE([model hasItem:item1]);
+  NSIndexPath* indexPath1 = [model indexPathForItem:item1];
   EXPECT_EQ(0, indexPath1.section);
   EXPECT_EQ(1, indexPath1.item);
 
-  NSIndexPath* indexPath4 = [model indexPathForItem:item4
-                            inSectionWithIdentifier:SectionIdentifierWeasley];
+  EXPECT_TRUE([model hasItem:item4]);
+  NSIndexPath* indexPath4 = [model indexPathForItem:item4];
   EXPECT_EQ(0, indexPath4.section);
   EXPECT_EQ(4, indexPath4.item);
+
+  EXPECT_FALSE([model hasItem:notAddedItem]);
 }
 
 TEST(CollectionViewModelTest, Headers) {
   CollectionViewModel* model = [[CollectionViewModel alloc] init];
 
   [model addSectionWithIdentifier:SectionIdentifierCheese];
   CollectionViewItem* cheeseHeader =
       [[CollectionViewItem alloc] initWithType:ItemTypeCheeseHeader];
   [model setHeader:cheeseHeader
       forSectionWithIdentifier:SectionIdentifierCheese];
@@ skipping 45 matching lines @@
 
   EXPECT_FALSE([model footerForSectionWithIdentifier:SectionIdentifierCheese]);
   EXPECT_FALSE([model footerForSection:cheeseSection]);
 
   EXPECT_EQ(weasleyFooter,
             [model footerForSectionWithIdentifier:SectionIdentifierWeasley]);
   EXPECT_EQ(weasleyFooter, [model footerForSection:weasleySection]);
 }
 
 }  // namespace