Topsites become keyedService based.

chrome/browser/history/chrome_history_client.h

Index: chrome/browser/history/chrome_history_client.h
diff --git a/chrome/browser/history/chrome_history_client.h b/chrome/browser/history/chrome_history_client.h
index fbaffc0e9cbb8ff747137dd451f753cab5dc1cac..c5ca702279a70d9a3ea35857b852a27cc1da269d 100644
--- a/chrome/browser/history/chrome_history_client.h
+++ b/chrome/browser/history/chrome_history_client.h
@@ -6,6 +6,7 @@
 #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"
 
@@ -45,17 +46,7 @@ class ChromeHistoryClient : public history::HistoryClient,
   // 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);
 };