ntp_tiles: Migrate to multi-observer model

components/ntp_tiles/most_visited_sites.h

 // Copyright 2013 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_TILES_MOST_VISITED_SITES_H_
 #define COMPONENTS_NTP_TILES_MOST_VISITED_SITES_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "base/scoped_observer.h"
 #include "base/strings/string16.h"
 #include "components/history/core/browser/history_types.h"
 #include "components/history/core/browser/top_sites_observer.h"
 #include "components/ntp_tiles/ntp_tile.h"
 #include "components/ntp_tiles/popular_sites.h"
 #include "components/suggestions/proto/suggestions.pb.h"
 #include "components/suggestions/suggestions_service.h"
 #include "url/gurl.h"
 
@@ skipping 43 matching lines @@
   virtual std::vector<Whitelist> whitelists() = 0;
 
   // If true, be conservative about suggesting sites from outside sources.
   virtual bool IsChildProfile() = 0;
 };
 
 // Tracks the list of most visited sites and their thumbnails.
 class MostVisitedSites : public history::TopSitesObserver,
                          public MostVisitedSitesSupervisor::Observer {
  public:
-  // The observer to be notified when the list of most visited sites changes.
+  // Observer to be notified when the list of most visited sites changes.
   class Observer {
    public:
     virtual void OnMostVisitedURLsAvailable(const NTPTilesVector& tiles) = 0;
     virtual void OnIconMadeAvailable(const GURL& site_url) = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
   // Construct a MostVisitedSites instance.
   //
   // |prefs| and |suggestions| are required and may not be null. |top_sites|,
   // |popular_sites|, and |supervisor| are optional and if null the associated
   // features will be disabled.
+  //
+  // Clients must call Refresh() to fetch the initial tiles.
   MostVisitedSites(PrefService* prefs,
                    scoped_refptr<history::TopSites> top_sites,
                    suggestions::SuggestionsService* suggestions,
                    std::unique_ptr<PopularSites> popular_sites,
                    std::unique_ptr<IconCacher> icon_cacher,
                    std::unique_ptr<MostVisitedSitesSupervisor> supervisor);
 
   ~MostVisitedSites() override;
 
-  // Sets the observer, and immediately fetches the current suggestions.
-  // Does not take ownership of |observer|, which must outlive this object and
-  // must not be null.
-  void SetMostVisitedURLsObserver(Observer* observer, int num_sites);
+  // Observer registration.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
 
-  // Requests an asynchronous refresh of the suggestions. Notifies the observer
+  // Requests an asynchronous refresh of the suggestions. Notifies the observers
   // once the request completes.

[sfiera, 2017/01/18 09:58:33]

This is now also necessary after every AddObserver() call, right? (there is no
way to get the current state, only updates)

   void Refresh();
 
+  // Blacklist manipulation.
   void AddOrRemoveBlacklistedUrl(const GURL& url, bool add_url);
   void ClearBlacklistedUrls();
 
   // MostVisitedSitesSupervisor::Observer implementation.
   void OnBlockedSitesChanged() override;
 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
   // Workhorse for SaveNewTiles. Implemented as a separate static and public
   // method for ease of testing.
@@ skipping 26 matching lines @@
 
   // Takes the personal and whitelist tiles and creates popular tiles if
   // necessary.
   NTPTilesVector CreatePopularSitesTiles(const NTPTilesVector& personal_tiles,
                                          const NTPTilesVector& whitelist_tiles);
 
   // Takes the personal tiles, creates and merges in whitelist and popular tiles
   // if appropriate, and saves the new tiles.
   void SaveNewTiles(NTPTilesVector personal_tiles);
 
-  // Notifies the observer about the availability of tiles.
+  // Notifies the observers about the availability of tiles.
   // Also records impressions UMA if not done already.
-  void NotifyMostVisitedURLsObserver();
+  void NotifyMostVisitedURLsObservers();
 
   void OnPopularSitesAvailable(bool success);
 
   void OnIconMadeAvailable(const GURL& site_url, bool newly_available);
 
   // history::TopSitesObserver implementation.
   void TopSitesLoaded(history::TopSites* top_sites) override;
   void TopSitesChanged(history::TopSites* top_sites,
                        ChangeReason change_reason) override;
 
   PrefService* prefs_;
   scoped_refptr<history::TopSites> top_sites_;
   suggestions::SuggestionsService* suggestions_service_;
   std::unique_ptr<PopularSites> const popular_sites_;
   std::unique_ptr<IconCacher> const icon_cacher_;
   std::unique_ptr<MostVisitedSitesSupervisor> supervisor_;
 
-  Observer* observer_;
-
-  // The maximum number of most visited sites to return.
-  int num_sites_;
+  base::ObserverList<Observer> observer_list_;
 
   std::unique_ptr<
       suggestions::SuggestionsService::ResponseCallbackList::Subscription>
       suggestions_subscription_;
 
   ScopedObserver<history::TopSites, history::TopSitesObserver>
       top_sites_observer_;
 
   // The main source of personal tiles - either TOP_SITES or SUGGESTIONS_SEVICE.
   NTPTileSource mv_source_;
 
   NTPTilesVector current_tiles_;
 
   // For callbacks may be run after destruction, used exclusively for TopSites
   // (since it's used to detect whether there's a query in flight).
   base::WeakPtrFactory<MostVisitedSites> top_sites_weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MostVisitedSites);
 };
 
 }  // namespace ntp_tiles
 
 #endif  // COMPONENTS_NTP_TILES_MOST_VISITED_SITES_H_