[NTP Snippets] Introduce ContentSuggestion::ID

components/ntp_snippets/category_factory.h

Index: components/ntp_snippets/category_factory.h
diff --git a/components/ntp_snippets/category_factory.h b/components/ntp_snippets/category_factory.h
index db134d24d226401010c5d0667d8ca54e3bfe0c66..c3941eaea2f31949c00d11fac2e87bff6ce17732 100644
--- a/components/ntp_snippets/category_factory.h
+++ b/components/ntp_snippets/category_factory.h
@@ -44,23 +44,6 @@ class CategoryFactory {
   // |FromRemoteCategory|.
   bool CompareCategories(const Category& left, const Category& right) const;
 
-  // TODO(treib): Remove the following 3 functions from here once we move to a
-  // more structured identification than the unique_id string and thus once we
-  // eliminate these functions. See crbug.com/649048.
-
-  // Creates a unique ID. The given |within_category_id| must be unique among
-  // all suggestion IDs from this provider for the given |category|. This method
-  // combines it with the |category| to form an ID that is unique
-  // application-wide, because this provider is the only one that provides
-  // suggestions for that category.
-  std::string MakeUniqueID(Category category,
-                           const std::string& within_category_id) const;
-
-  // Reverse functions for MakeUniqueID()
-  Category GetCategoryFromUniqueID(const std::string& unique_id);
-  std::string GetWithinCategoryIDFromUniqueID(
-      const std::string& unique_id) const;
-
  private:
   bool CategoryExists(int id);
   void AddKnownCategory(KnownCategories known_category);