Topsites become keyedService based.

chrome/browser/history/top_sites.h

Index: chrome/browser/history/top_sites.h
diff --git a/chrome/browser/history/top_sites.h b/chrome/browser/history/top_sites.h
index 96a82b0b2428e2dd78602166818229b92a47663b..c4f36172415afcc5875e49ab744db999f77c9a88 100644
--- a/chrome/browser/history/top_sites.h
+++ b/chrome/browser/history/top_sites.h
@@ -8,12 +8,12 @@
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
-#include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "components/history/core/browser/history_types.h"
 #include "components/history/core/browser/top_sites_observer.h"
 #include "components/history/core/common/thumbnail_score.h"
+#include "components/keyed_service/core/refcounted_keyed_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/image/image.h"
@@ -37,9 +37,8 @@ class TopSitesCache;
 //
 // Some methods should only be called from the UI thread (see method
 // descriptions below). All others are assumed to be threadsafe.
-class TopSites
-    : public base::RefCountedThreadSafe<TopSites>,
-      public content::NotificationObserver {
+class TopSites : public RefcountedKeyedService,
+                 public content::NotificationObserver {
  public:
   TopSites();