Topsites become keyedService based.

chrome/browser/history/chrome_history_client.h

 // Copyright 2014 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_HISTORY_CHROME_HISTORY_CLIENT_H_
 #define CHROME_BROWSER_HISTORY_CHROME_HISTORY_CLIENT_H_
 
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"
 #include "components/history/core/browser/history_client.h"
 #include "components/history/core/browser/top_sites_observer.h"
 
 class BookmarkModel;
 class HistoryService;
 class Profile;
 
 namespace history {
 class TopSites;
 }
 
 // This class implements history::HistoryClient to abstract operations that
 // depend on Chrome environment.
 class ChromeHistoryClient : public history::HistoryClient,
                             public history::TopSitesObserver {
  public:
   explicit ChromeHistoryClient(BookmarkModel* bookmark_model,
                                Profile* profile,
                                history::TopSites* top_sites);

[Bernhard Bauer, 2015/01/08 10:22:05]

This should take a const scoped_refptr<>& now.

[Jitu( very slow this week), 2015/01/12 11:30:07]

Done.

   ~ChromeHistoryClient() override;
 
   // history::HistoryClient:
   void BlockUntilBookmarksLoaded() override;
   bool IsBookmarked(const GURL& url) override;
   void GetBookmarks(std::vector<history::URLAndTitle>* bookmarks) override;
   void NotifyProfileError(sql::InitStatus init_status) override;
   bool ShouldReportDatabaseError() override;
 
   // KeyedService:
   void Shutdown() override;
 
   // TopSitesObserver:
   void TopSitesLoaded(history::TopSites* top_sites) override;
   void TopSitesChanged(history::TopSites* top_sites) override;
 
  private:
   // The BookmarkModel, this should outlive ChromeHistoryClient.
   BookmarkModel* bookmark_model_;
   Profile* profile_;
-  // The TopSites object is owned by the Profile (see
-  // chrome/browser/profiles/profile_impl.h)
-  // and lazily constructed by the  getter.
-  // ChromeHistoryClient is a KeyedService linked to the Profile lifetime by the
-  // ChromeHistoryClientFactory (which is a BrowserContextKeyedServiceFactory).
-  // Before the Profile is destroyed, all the KeyedService Shutdown methods are
-  // called, and the Profile is fully constructed before any of the KeyedService
-  // can  be constructed. The TopSites does not use the HistoryService nor the
-  // HistoryClient during construction (it uses it later, but supports getting
-  // an NULL  pointer).
-  history::TopSites* top_sites_;
+  scoped_refptr<history::TopSites> top_sites_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeHistoryClient);
 };
 
 #endif  // CHROME_BROWSER_HISTORY_CHROME_HISTORY_CLIENT_H_