Add a message to empty ContentSuggestions sections

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

Index: ios/chrome/browser/ui/content_suggestions/content_suggestion.h
diff --git a/ios/chrome/browser/ui/content_suggestions/content_suggestion.h b/ios/chrome/browser/ui/content_suggestions/content_suggestion.h
index 5470c116c267e5e1484cce666991258978cbefe6..97742bbbe73c06ceed6254ab1b5d85ec9ba74097 100644
--- a/ios/chrome/browser/ui/content_suggestions/content_suggestion.h
+++ b/ios/chrome/browser/ui/content_suggestions/content_suggestion.h
@@ -17,6 +17,10 @@ class GURL;
 
 // Enum defining the type of a ContentSuggestions.
 typedef NS_ENUM(NSInteger, ContentSuggestionType) {
+  // Use this type to pass information about an empty section. Suggestion of
+  // this type are empty and should not be displayed. The informations to be
+  // displayed are contained in the SectionInfo.
+  ContentSuggestionTypeEmpty,
   ContentSuggestionTypeArticle
 };