Cleanup ContentSuggestions, removing unused functions

ios/chrome/browser/ui/content_suggestions/content_suggestions_commands.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_COMMANDS_H_
 #define IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_COMMANDS_H_
 
 @class ContentSuggestionsArticleItem;
 class GURL;
 
 // Commands protocol for the ContentSuggestionsViewController.
 @protocol ContentSuggestionsCommands
 
-// Adds a new empty SuggestionItem.
-- (void)addEmptyItem;
 // Opens the Reading List.
 - (void)openReadingList;
 // Opens the first page of the Reading List.
 - (void)openFirstPageOfReadingList;
 // Opens the favicon associated with the cell with the |index|.
 - (void)openFaviconAtIndex:(NSInteger)index;
 // Opens the |URL|.
 - (void)openURL:(const GURL&)URL;
 // Displays a context menu for opening the |articleItem|.
 - (void)displayContextMenuForArticle:(ContentSuggestionsArticleItem*)articleItem
                              atPoint:(CGPoint)touchLocation;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_COMMANDS_H_