[NTP Snippets] Introduce ContentSuggestion::ID

components/ntp_snippets/content_suggestions_service.h

Index: components/ntp_snippets/content_suggestions_service.h
diff --git a/components/ntp_snippets/content_suggestions_service.h b/components/ntp_snippets/content_suggestions_service.h
index 8c4a4f75b70e8be5e9f301fec345c1c42f535635..045785f06e5f382762e9e681438e0107143e933b 100644
--- a/components/ntp_snippets/content_suggestions_service.h
+++ b/components/ntp_snippets/content_suggestions_service.h
@@ -63,12 +63,12 @@ class ContentSuggestionsService : public KeyedService,
     // Fired when a suggestion has been invalidated. The UI must immediately
     // clear the suggestion even from open NTPs. Invalidation happens, for
     // example, when the content that the suggestion refers to is gone.
-    // Note that this event may be fired even if the corresponding |category| is
+    // Note that this event may be fired even if the corresponding category is
     // not currently AVAILABLE, because open UIs may still be showing the
     // suggestion that is to be removed. This event may also be fired for
     // |suggestion_id|s that never existed and should be ignored in that case.
-    virtual void OnSuggestionInvalidated(Category category,
-                                         const std::string& suggestion_id) = 0;
+    virtual void OnSuggestionInvalidated(
+        const ContentSuggestion::ID& suggestion_id) = 0;
 
     // Sent when the service is shutting down. After the service has shut down,
     // it will not provide any data anymore, though calling the getters is still
@@ -114,12 +114,12 @@ class ContentSuggestionsService : public KeyedService,
   // runs the |callback|. If that suggestion doesn't exist or the fetch fails,
   // the callback gets an empty image. The callback will not be called
   // synchronously.
-  void FetchSuggestionImage(const std::string& suggestion_id,
+  void FetchSuggestionImage(const ContentSuggestion::ID& suggestion_id,
                             const ImageFetchedCallback& callback);
 
   // Dismisses the suggestion with the given |suggestion_id|, if it exists.
   // This will not trigger an update through the observers.
-  void DismissSuggestion(const std::string& suggestion_id);
+  void DismissSuggestion(const ContentSuggestion::ID& suggestion_id);
 
   // Dismisses the given |category|, if it exists.
   // This will not trigger an update through the observers.
@@ -193,9 +193,9 @@ class ContentSuggestionsService : public KeyedService,
   void OnCategoryStatusChanged(ContentSuggestionsProvider* provider,
                                Category category,
                                CategoryStatus new_status) override;
-  void OnSuggestionInvalidated(ContentSuggestionsProvider* provider,
-                               Category category,
-                               const std::string& suggestion_id) override;
+  void OnSuggestionInvalidated(
+      ContentSuggestionsProvider* provider,
+      const ContentSuggestion::ID& suggestion_id) override;
 
   // history::HistoryServiceObserver implementation.
   void OnURLsDeleted(history::HistoryService* history_service,
@@ -214,8 +214,7 @@ class ContentSuggestionsService : public KeyedService,
 
   // Removes a suggestion from the local store |suggestions_by_category_|, if it
   // exists. Returns true if a suggestion was removed.
-  bool RemoveSuggestionByID(Category category,
-                            const std::string& suggestion_id);
+  bool RemoveSuggestionByID(const ContentSuggestion::ID& suggestion_id);
 
   // Fires the OnCategoryStatusChanged event for the given |category|.
   void NotifyCategoryStatusChanged(Category category);