Make TopSites a RefcountedKeyedService

chrome/browser/history/top_sites_impl.cc

Index: chrome/browser/history/top_sites_impl.cc
diff --git a/chrome/browser/history/top_sites_impl.cc b/chrome/browser/history/top_sites_impl.cc
index 5d1a78d1ffce9c33f6fdbbeab34cc5e977e8e951..6d332bbb93cecb57d4afeec98f9a17275757c02b 100644
--- a/chrome/browser/history/top_sites_impl.cc
+++ b/chrome/browser/history/top_sites_impl.cc
@@ -373,13 +373,16 @@ void TopSitesImpl::ClearBlacklistedURLs() {
   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