Use pipe as ID separator and add inverse functions for MakeUniqueID

components/ntp_snippets/content_suggestions_provider.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 COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_PROVIDER_H_
 #define COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_PROVIDER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 92 matching lines @@
       const std::vector<ContentSuggestionsCategory>& provided_categories);
   virtual ~ContentSuggestionsProvider();
 
   // 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.
   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_;
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_PROVIDER_H_