[ios] Fix clean shutdown of Chrome on iOS.

ios/chrome/app/spotlight/topsites_spotlight_manager.mm

 // Copyright 2015 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/app/spotlight/topsites_spotlight_manager.h"
 
 #include <memory>
 
 #include "base/memory/ref_counted.h"
 #include "base/strings/sys_string_conversions.h"
@@ skipping 75 matching lines @@
     (const suggestions::SuggestionsProfile&)suggestions_profile;
 
 @end
 
 class SpotlightTopSitesCallbackBridge
     : public base::SupportsWeakPtr<SpotlightTopSitesCallbackBridge> {
  public:
   explicit SpotlightTopSitesCallbackBridge(TopSitesSpotlightManager* owner)
       : owner_(owner) {}
 
-  SpotlightTopSitesCallbackBridge() {}
+  ~SpotlightTopSitesCallbackBridge() {}
 
   void OnMostVisitedURLsAvailable(const history::MostVisitedURLList& data) {
     [owner_ onMostVisitedURLsAvailable:data];
   }
 
  private:
   __weak TopSitesSpotlightManager* owner_;
 };
 
 class SpotlightTopSitesBridge : public history::TopSitesObserver {
  public:
-  explicit SpotlightTopSitesBridge(TopSitesSpotlightManager* owner)
-      : owner_(owner) {
-    owner.topSites->AddObserver(this);
+  SpotlightTopSitesBridge(TopSitesSpotlightManager* owner,
+                          history::TopSites* top_sites)
+      : owner_(owner), top_sites_(top_sites) {
+    top_sites->AddObserver(this);
   };
 
   ~SpotlightTopSitesBridge() override {
-    owner_.topSites->RemoveObserver(this);
+    top_sites_->RemoveObserver(this);
+    top_sites_ = nullptr;
   };
 
   void TopSitesLoaded(history::TopSites* top_sites) override {}
 
   void TopSitesChanged(history::TopSites* top_sites,
                        ChangeReason change_reason) override {
     [owner_ updateAllTopSitesSpotlightItems];
   }
 
  private:
   __weak TopSitesSpotlightManager* owner_;
+  history::TopSites* top_sites_;
 };
 
 class SpotlightSuggestionsBridge
     : public base::SupportsWeakPtr<SpotlightSuggestionsBridge> {
  public:
   explicit SpotlightSuggestionsBridge(TopSitesSpotlightManager* owner)
       : owner_(owner) {}
 
-  SpotlightSuggestionsBridge() {}
+  ~SpotlightSuggestionsBridge() {}
 
   void OnSuggestionsProfileAvailable(
       const suggestions::SuggestionsProfile& suggestions_profile) {
     [owner_ onSuggestionsProfileAvailable:suggestions_profile];
   }
 
  private:
   __weak TopSitesSpotlightManager* owner_;
 };
 
@@ skipping 18 matching lines @@
 - (instancetype)
 initWithLargeIconService:(favicon::LargeIconService*)largeIconService
                 topSites:(scoped_refptr<history::TopSites>)topSites
            bookmarkModel:(bookmarks::BookmarkModel*)bookmarkModel
       profileSyncService:(browser_sync::ProfileSyncService*)syncService
       suggestionsService:(suggestions::SuggestionsService*)suggestionsService {
   self = [super initWithLargeIconService:largeIconService
                                   domain:spotlight::DOMAIN_TOPSITES];
   if (self) {
     _topSites = topSites;
-    _topSitesBridge.reset(new SpotlightTopSitesBridge(self));
+    _topSitesBridge.reset(new SpotlightTopSitesBridge(self, _topSites.get()));
     _topSitesCallbackBridge.reset(new SpotlightTopSitesCallbackBridge(self));
     _bookmarkModel = bookmarkModel;
     _isReindexPending = false;
     if (syncService && suggestionsService) {
       _suggestionsBridge.reset(new SpotlightSuggestionsBridge(self));
       _syncService = syncService;
       _suggestionService = suggestionsService;
       _suggestionsServiceResponseSubscription = _suggestionService->AddCallback(
           base::Bind(&SpotlightSuggestionsBridge::OnSuggestionsProfileAvailable,
                      _suggestionsBridge->AsWeakPtr()));
@@ skipping 100 matching lines @@
 }
 
 #pragma mark -
 #pragma mark SyncObserverModelBridge
 
 - (void)onSyncStateChanged {
   [self updateAllTopSitesSpotlightItems];
 }
 
 @end