Add a message to empty ContentSuggestions sections

ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.h

 // 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.
 
 #ifndef IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_COLLECTION_UPDATER_H_
 #define IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_COLLECTION_UPDATER_H_
 
 #import <UIKit/UIKit.h>
 
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestion.h"
@@ skipping 23 matching lines @@
 // Returns the ContentSuggestionType associated with this item.
 - (ContentSuggestionType)contentSuggestionTypeForItem:(CollectionViewItem*)item;
 
 // Adds the sections for the |suggestions| to the model and returns their
 // indices.
 - (NSIndexSet*)addSectionsForSuggestionsToModel:
     (NSArray<ContentSuggestion*>*)suggestions;
 
 // Adds the |suggestions| to the model and returns their index paths.
 // The caller must ensure the corresponding sections have been added to the
 // model.

[lpromero, 2017/03/23 10:54:37]

Maybe mention that if a section has no items, the empty item is added?

[gambard, 2017/03/23 15:25:49]

The empty suggestion is a type of suggestion, with a corresponding item
determined by the updater.
So if you have an empty suggestion in your array, the updater will add the
corresponding item in the same way it will do it for the other type of
suggestions.
If you don't have an empty item but a section is empty, the updater will do
nothing. So for me this comment reflect what will happen.

 - (NSArray<NSIndexPath*>*)addSuggestionsToModel:
     (NSArray<ContentSuggestion*>*)suggestions;
 
+// Adds the empty item for this section.

[lpromero, 2017/03/23 10:54:37]

s/for/to? If you change, change also the method name.

[gambard, 2017/03/23 15:25:49]

Done.

+- (void)addEmptyItemForSection:(NSInteger)section;

[lpromero, 2017/03/23 10:54:37]

Please add unittests.

[gambard, 2017/03/23 15:25:49]

Done.

+
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_COLLECTION_UPDATER_H_