Use pipe as ID separator and add inverse functions for MakeUniqueID

components/ntp_snippets/content_suggestions_provider.h

Index: components/ntp_snippets/content_suggestions_provider.h
diff --git a/components/ntp_snippets/content_suggestions_provider.h b/components/ntp_snippets/content_suggestions_provider.h
index 8d0b5dd7e5d6c38ae55581b5ca84299aae71dac0..43f211bd96a430c9a2517c35e597ee29697e385f 100644
--- a/components/ntp_snippets/content_suggestions_provider.h
+++ b/components/ntp_snippets/content_suggestions_provider.h
@@ -110,6 +110,11 @@ class ContentSuggestionsProvider {
   // suggestions for that category.
   static std::string MakeUniqueID(ContentSuggestionsCategory category,
                                   const std::string& within_category_id);
+  // Reverse functions for MakeUniqueID()
+  static ContentSuggestionsCategory GetCategoryFromUniqueID(
+      const std::string& unique_id);
+  static std::string GetWithinCategoryIDFromUniqueID(
+      const std::string& unique_id);
 
  private:
   const std::vector<ContentSuggestionsCategory> provided_categories_;