Remove TopSites notification in favor of Observers

chrome/browser/ui/webui/ntp/suggestions_page_handler.h

 // Copyright (c) 2012 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 CHROME_BROWSER_UI_WEBUI_NTP_SUGGESTIONS_PAGE_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_NTP_SUGGESTIONS_PAGE_HANDLER_H_
 
 #include <string>
 
+#include "base/scoped_observer.h"
 #include "chrome/browser/ui/webui/ntp/suggestions_combiner.h"
 #include "components/history/core/browser/history_types.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
+#include "components/history/core/browser/top_sites_observer.h"
 #include "content/public/browser/web_ui_message_handler.h"
 
 class GURL;
 class PageUsageData;
 
 namespace base {
 class ListValue;
 class Value;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 // The handler for Javascript messages related to the "suggestions" view.
 //
 // This class manages one preference:
 // - The URL blacklist: URLs we do not want to show in the thumbnails list.  It
 //   is a dictionary for quick access (it associates a dummy boolean to the URL
 //   string).
 class SuggestionsHandler : public content::WebUIMessageHandler,
-                           public content::NotificationObserver,
-                           public SuggestionsCombiner::Delegate {
+                           public SuggestionsCombiner::Delegate,
+                           public history::TopSitesObserver {
  public:
   SuggestionsHandler();
   ~SuggestionsHandler() override;
 
   // WebUIMessageHandler override and implementation.
   void RegisterMessages() override;
 
   // Callback for the "getSuggestions" message.
   void HandleGetSuggestions(const base::ListValue* args);
 
   // Callback for the "blacklistURLFromSuggestions" message.
   void HandleBlacklistURL(const base::ListValue* args);
 
   // Callback for the "removeURLsFromSuggestionsBlacklist" message.
   void HandleRemoveURLsFromBlacklist(const base::ListValue* args);
 
   // Callback for the "clearSuggestionsURLsBlacklist" message.
   void HandleClearBlacklist(const base::ListValue* args);
 
   // Callback for the "suggestedSitesAction" message.
   void HandleSuggestedSitesAction(const base::ListValue* args);
 
   // Callback for the "suggestedSitesSelected" message.
   void HandleSuggestedSitesSelected(const base::ListValue* args);
 
-  // content::NotificationObserver implementation.
-  void Observe(int type,
-               const content::NotificationSource& source,
-               const content::NotificationDetails& details) override;
+  // history::TopSitesObserver implementation.
+  void TopSitesLoaded(history::TopSites* top_sites) override;
+  void TopSitesChanged(history::TopSites* top_sites) override;
 
   // SuggestionsCombiner::Delegate implementation.
   void OnSuggestionsReady() override;
 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
  private:
   // Puts the passed URL in the blacklist (so it does not show as a thumbnail).
   void BlacklistURL(const GURL& url);
 
   // Returns the key used in url_blacklist_ for the passed |url|.
   std::string GetDictionaryKeyForURL(const std::string& url);
 
   // Sends pages_value_ to the javascript side to and resets page_value_.
   void SendPagesValue();
 
-  content::NotificationRegistrar registrar_;
+  // Scoped observer to help with TopSitesObserver registration.
+  ScopedObserver<history::TopSites, history::TopSitesObserver> scoped_observer_;
 
   // We pre-fetch the first set of result pages.  This variable is false until
   // we get the first getSuggestions() call.
   bool got_first_suggestions_request_;
 
   // Used to combine suggestions from various sources.
   scoped_ptr<SuggestionsCombiner> suggestions_combiner_;
 
   // Whether the user has viewed the 'suggested' pane.
   bool suggestions_viewed_;
 
   // Whether the user has performed a "tracked" action to leave the page or not.
   bool user_action_logged_;
 
   DISALLOW_COPY_AND_ASSIGN(SuggestionsHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_NTP_SUGGESTIONS_PAGE_HANDLER_H_