Refactor and extend SnippetsBridge for multi-section support

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 7f771b5f4130be52b298381096fe0155c603981e..a40b15c9d3c00bc07d2dcdc2c01999531763543c 100644
--- a/components/ntp_snippets/content_suggestions_service.h
+++ b/components/ntp_snippets/content_suggestions_service.h
@@ -36,11 +36,11 @@ class ContentSuggestionsService : public KeyedService,
 
   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