Make ShortcutsBackend a ProfileKeyedService.

chrome/browser/profiles/profile_impl.cc

Index: chrome/browser/profiles/profile_impl.cc
===================================================================
--- chrome/browser/profiles/profile_impl.cc	(revision 144929)
+++ chrome/browser/profiles/profile_impl.cc	(working copy)
@@ -42,6 +42,7 @@
 #include "chrome/browser/history/history.h"
 #include "chrome/browser/history/history_service_factory.h"
 #include "chrome/browser/history/shortcuts_backend.h"
+#include "chrome/browser/history/shortcuts_backend_factory.h"
 #include "chrome/browser/history/top_sites.h"
 #include "chrome/browser/instant/instant_controller.h"
 #include "chrome/browser/metrics/metrics_service.h"
@@ -796,13 +797,7 @@
 }
 
 history::ShortcutsBackend* ProfileImpl::GetShortcutsBackend() {
-  // This is called on one thread only - UI, so no magic is needed to protect
-  // against the multiple concurrent calls.
-  if (!shortcuts_backend_.get()) {
-    shortcuts_backend_ = new history::ShortcutsBackend(GetPath(), this);
-    CHECK(shortcuts_backend_->Init());
-  }
-  return shortcuts_backend_.get();
+  return ShortcutsBackendFactory::GetForProfile(this).get();
 }
 
 DownloadManagerDelegate* ProfileImpl::GetDownloadManagerDelegate() {