Add an ID to the ContentSuggestion

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

 // Copyright 2017 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_ARTICLE_ITEM_H_
 #define IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_ARTICLE_ITEM_H_
 
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
+#import "ios/chrome/browser/ui/content_suggestions/content_suggestion_id.h"
 #import "ios/third_party/material_components_ios/src/components/CollectionCells/src/MaterialCollectionCells.h"
 #include "url/gurl.h"
 
 // Item for an article in the suggestions.
-@interface ContentSuggestionsArticleItem : CollectionViewItem
+@interface ContentSuggestionsArticleItem
+    : CollectionViewItem<ContentSuggestionIDHolder>
 
 // Initialize an article with a |title|, a |subtitle|, an |image| and the |url|
 // to the full article. |type| is the type of the item.
 - (instancetype)initWithType:(NSInteger)type
                        title:(NSString*)title
                     subtitle:(NSString*)subtitle
                        image:(UIImage*)image
                          url:(const GURL&)url NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)initWithType:(NSInteger)type NS_UNAVAILABLE;
 
 @property(nonatomic, strong) UIImage* image;
 @property(nonatomic, readonly, assign) GURL articleURL;
 
 @end
 
 // Corresponding cell for an article in the suggestions.
 @interface ContentSuggestionsArticleCell : MDCCollectionViewCell
 
 @property(nonatomic, readonly, strong) UILabel* titleLabel;
 @property(nonatomic, readonly, strong) UILabel* subtitleLabel;
 @property(nonatomic, readonly, strong) UIImageView* imageView;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_ARTICLE_ITEM_H_