Add FetchMore to Content Suggestions Mediator

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

Index: ios/chrome/browser/ui/content_suggestions/content_suggestions_data_source.h
diff --git a/ios/chrome/browser/ui/content_suggestions/content_suggestions_data_source.h b/ios/chrome/browser/ui/content_suggestions/content_suggestions_data_source.h
index b02a64ac8181a240a70cbb9b9324c3840aa695d6..e54ea8c245038db021835afd7c9618c357a3cb9a 100644
--- a/ios/chrome/browser/ui/content_suggestions/content_suggestions_data_source.h
+++ b/ios/chrome/browser/ui/content_suggestions/content_suggestions_data_source.h
@@ -6,9 +6,13 @@
 #define IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_DATA_SOURCE_H_
 
 @class ContentSuggestion;
+@class ContentSuggestionIdentifier;
 @protocol ContentSuggestionsDataSink;
+@class ContentSuggestionsSectionInformation;
 @protocol ContentSuggestionsImageFetcher;
 
+typedef void (^MoreSuggestionsFetched)(NSArray<ContentSuggestion*>*);
+
 // DataSource for the content suggestions. Provides the suggestions data in a
 // format compatible with Objective-C.
 @protocol ContentSuggestionsDataSource
@@ -23,6 +27,16 @@
 // Returns an image updater for the suggestions provided by this data source.
 - (id<ContentSuggestionsImageFetcher>)imageFetcher;
 
+// Fetches additional contents. All the |knownSuggestions| must come from the
+// same |sectionInfo|. If the fetch was completed, the given |callback| is
+// called with the updated content.
+// This includes new and old data.
+- (void)fetchMoreSuggestionsKnowing:
+            (NSArray<ContentSuggestionIdentifier*>*)knownSuggestions
+                    fromSectionInfo:
+                        (ContentSuggestionsSectionInformation*)sectionInfo
+                           callback:(MoreSuggestionsFetched)callback;
+
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_DATA_SOURCE_H_