Refactor and extend SnippetsBridge for multi-section support

components/ntp_snippets/content_suggestions_service.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_SERVICE_H_
 #define COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 18 matching lines @@
 // Retrieves suggestions from a number of ContentSuggestionsProviders and serves
 // them grouped into categories. There can be at most one provider per category.
 class ContentSuggestionsService : public KeyedService,
                                   public ContentSuggestionsProvider::Observer {
  public:
   using ImageFetchedCallback =
       base::Callback<void(const std::string& suggestion_id, const gfx::Image&)>;
 
   class Observer {
    public:
-    // Fired every time the service receives a new set of data, replacing any
-    // previously available data (though in most cases there will be an overlap
-    // and only a few changes within the data). The new data is then available
-    // through the getters of the service.
-    virtual void OnNewSuggestions() = 0;
+    // Fired every time the service receives a new set of data for the given
+    // |category|, replacing any previously available data (though in most cases
+    // there will be an overlap and only a few changes within the data). The new
+    // data is then available through |GetSuggestionsForCategory(category)|.
+    virtual void OnNewSuggestions(Category category) = 0;
 
     // Fired when the status of a suggestions category changed. When the status
     // changes to an unavailable status, the suggestions of the respective
     // category have been invalidated, which means that they must no longer be
     // displayed to the user. The UI must immediately clear any suggestions of
     // that category.
     virtual void OnCategoryStatusChanged(Category category,
                                          CategoryStatus new_status) = 0;
 
     // Sent when the service is shutting down. After the service has shut down,
@@ skipping 157 matching lines @@
   // background fetching and debugging calls to it. If the NTPSnippetsService is
   // loaded, it is also present in |providers_|, otherwise this is a nullptr.
   NTPSnippetsService* ntp_snippets_service_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentSuggestionsService);
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_CONTENT_SUGGESTIONS_SERVICE_H_