Make TopSites a RefcountedKeyedService

chrome/browser/history/top_sites_impl.cc

 // Copyright (c) 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.
 
 #include "chrome/browser/history/top_sites_impl.h"
 
 #include <algorithm>
 #include <set>
 
 #include "base/bind.h"
@@ skipping 355 matching lines @@
   {
     DictionaryPrefUpdate update(profile_->GetPrefs(),
                                 prefs::kNtpMostVisitedURLsBlacklist);
     base::DictionaryValue* blacklist = update.Get();
     blacklist->Clear();
   }
   ResetThreadSafeCache();
   NotifyTopSitesChanged();
 }
 
-void TopSitesImpl::Shutdown() {
+void TopSitesImpl::ShutdownOnUIThread() {
   profile_ = NULL;
   // Cancel all requests so that the service doesn't callback to us after we've
   // invoked Shutdown (this could happen if we have a pending request and
   // Shutdown is invoked).
   cancelable_task_tracker_.TryCancelAll();
-  backend_->Shutdown();
+  registrar_.RemoveAll();
+  // The TopSitesBackend may not be created during unit tests.
+  if (backend_)
+    backend_->Shutdown();
 }
 
 // static
 void TopSitesImpl::DiffMostVisited(const MostVisitedURLList& old_list,
                                    const MostVisitedURLList& new_list,
                                    TopSitesDelta* delta) {
 
   // Add all the old URLs for quick lookup. This maps URLs to the corresponding
   // index in the input.
   std::map<GURL, size_t> all_old_urls;
@@ skipping 526 matching lines @@
       base::TimeDelta::FromSeconds(kUpdateIntervalSecs));
 }
 
 void TopSitesImpl::OnTopSitesAvailableFromHistory(
     const MostVisitedURLList* pages) {
   DCHECK(pages);
   SetTopSites(*pages);
 }
 
 }  // namespace history