ntp_tiles: Migrate to multi-observer model

ios/chrome/browser/ui/ntp/google_landing_controller.mm

 // 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.
 
 #import "ios/chrome/browser/ui/ntp/google_landing_controller.h"
 
 #include <algorithm>
 
 #include "base/i18n/case_conversion.h"
 #import "base/ios/weak_nsobject.h"
@@ skipping 103 matching lines @@
 - (void)onIconMadeAvailable:(const GURL&)siteUrl;
 @end
 
 namespace google_landing {
 
 // MostVisitedSitesObserverBridge allow registration as a
 // MostVisitedSites::Observer.
 class MostVisitedSitesObserverBridge
     : public ntp_tiles::MostVisitedSites::Observer {
  public:
-  MostVisitedSitesObserverBridge(GoogleLandingController* owner);
+  MostVisitedSitesObserverBridge(
+      GoogleLandingController* owner,
+      ntp_tiles::MostVisitedSites* most_visited_sites);
   ~MostVisitedSitesObserverBridge() override;
 
   // MostVisitedSites::Observer implementation.
   void OnMostVisitedURLsAvailable(
       const ntp_tiles::NTPTilesVector& most_visited) override;
   void OnIconMadeAvailable(const GURL& site_url) override;
 
  private:
   GoogleLandingController* _owner;
+  ntp_tiles::MostVisitedSites* _most_visited_sites;  // weak
 };
 
 MostVisitedSitesObserverBridge::MostVisitedSitesObserverBridge(
-    GoogleLandingController* owner)
-    : _owner(owner) {}
+    GoogleLandingController* owner,
+    ntp_tiles::MostVisitedSites* most_visited_sites)
+    : _owner(owner), _most_visited_sites(most_visited_sites) {
+  _most_visited_sites->AddObserver(this);
+}
 
-MostVisitedSitesObserverBridge::~MostVisitedSitesObserverBridge() {}
+MostVisitedSitesObserverBridge::~MostVisitedSitesObserverBridge() {
+  _most_visited_sites->RemoveObserver(this);
+}
 
 void MostVisitedSitesObserverBridge::OnMostVisitedURLsAvailable(
     const ntp_tiles::NTPTilesVector& tiles) {
   [_owner onMostVisitedURLsAvailable:tiles];
 }
 
 void MostVisitedSitesObserverBridge::OnIconMadeAvailable(const GURL& site_url) {
   [_owner onIconMadeAvailable:site_url];
 }
 
@@ skipping 108 matching lines @@
   // Tap and swipe gesture recognizers when the omnibox is focused.
   base::scoped_nsobject<UITapGestureRecognizer> _tapGestureRecognizer;
   base::scoped_nsobject<UISwipeGestureRecognizer> _swipeGestureRecognizer;
 
   // Handles displaying the context menu for all form factors.
   base::scoped_nsobject<ContextMenuCoordinator> _contextMenuCoordinator;
 
   // What's new promo.
   std::unique_ptr<NotificationPromoWhatsNew> _notification_promo;
 
+  std::unique_ptr<ntp_tiles::MostVisitedSites> _most_visited_sites;
+
   // A MostVisitedSites::Observer bridge object to get notified of most visited
   // sites changes.
   std::unique_ptr<google_landing::MostVisitedSitesObserverBridge>
       _most_visited_observer_bridge;
 
-  std::unique_ptr<ntp_tiles::MostVisitedSites> _most_visited_sites;
-
   // URL of the last deleted most viewed entry. If present the UI to restore it
   // is shown.
   base::scoped_nsobject<NSURL> _deletedUrl;
 
   // Listen for default search engine changes.
   std::unique_ptr<google_landing::SearchEngineObserver> _observer;
   TemplateURLService* _templateURLService;  // weak
 
   // |YES| if the view has finished its first layout. This is useful when
   // determining if the view has sized itself for tablet.
@@ skipping 638 matching lines @@
               withReuseIdentifier:@"whatsNew"];
   [_mostVisitedView registerClass:[NewTabPageHeaderView class]
        forSupplementaryViewOfKind:UICollectionElementKindSectionHeader
               withReuseIdentifier:@"header"];
   [_mostVisitedView setAccessibilityIdentifier:@"Google Landing"];
 
   [_view addSubview:_mostVisitedView];
   _most_visited_sites =
       IOSMostVisitedSitesFactory::NewForBrowserState(_browserState);
   _most_visited_observer_bridge.reset(
-      new google_landing::MostVisitedSitesObserverBridge(self));
-  _most_visited_sites->SetMostVisitedURLsObserver(
-      _most_visited_observer_bridge.get(), kMaxNumMostVisitedFavicons);
+      new google_landing::MostVisitedSitesObserverBridge(
+          self, _most_visited_sites.get()));
+  _most_visited_sites->Refresh();
 }
 
 - (void)updateSearchField {
   NSArray* constraints =
       @[ _hintLabelLeadingConstraint, _voiceTapTrailingConstraint ];
   [_headerView updateSearchField:_searchTapTarget
                 withInitialFrame:[self searchFieldFrame]
               subviewConstraints:constraints
                        forOffset:[_mostVisitedView contentOffset].y];
 }
@@ skipping 145 matching lines @@
                    tileType:(ntp_tiles::metrics::MostVisitedTileType)tileType {
   new_tab_page_uma::RecordAction(
       _browserState, new_tab_page_uma::ACTION_OPENED_MOST_VISITED_ENTRY);
   base::RecordAction(UserMetricsAction("MobileNTPMostVisited"));
   const ntp_tiles::NTPTile& tile = _mostVisitedData[visitedIndex];
   ntp_tiles::metrics::RecordTileClick(visitedIndex, tile.source, tileType);
 }
 
 - (void)onMostVisitedURLsAvailable:(const ntp_tiles::NTPTilesVector&)data {
   _mostVisitedData = data;
+  if (_mostVisitedData.size() > kMaxNumMostVisitedFavicons)

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

We're resizing to save memory, but it's not related to the number of tiles we're
actually going to show, is it? I think it would be good to have a comment in
this function explaining that we might show fewer than _mostVisitedData.size()
tiles, and a TODO to correct the impressions metrics accordingly (ios will make
you create a bug for a TODO; P3/sfiera is OK).

+    _mostVisitedData.resize(kMaxNumMostVisitedFavicons);
+
   [self reloadData];
 
-  if (data.size() && !_recordedPageImpression) {
+  if (_mostVisitedData.size() && !_recordedPageImpression) {
     _recordedPageImpression = YES;
     std::vector<ntp_tiles::metrics::TileImpression> tiles;
-    for (const ntp_tiles::NTPTile& ntpTile : data) {
+    for (const ntp_tiles::NTPTile& ntpTile : _mostVisitedData) {
       tiles.emplace_back(ntpTile.source, ntp_tiles::metrics::UNKNOWN_TILE_TYPE,
                          ntpTile.url);
     }
     ntp_tiles::metrics::RecordPageImpression(
         tiles, GetApplicationContext()->GetRapporServiceImpl());
   }
 }
 
 - (void)onIconMadeAvailable:(const GURL&)siteUrl {
   for (size_t i = 0; i < [self numberOfItems]; ++i) {
@@ skipping 622 matching lines @@
   if (!view) {
     return nil;
   }
   if ([view isKindOfClass:aClass]) {
     return view;
   }
   return [self nearestAncestorOfView:[view superview] withClass:aClass];
 }
 
 @end