Remove BrowserThread::UnsafeGetBrowserThread, add UnsafeGetMessageLoopForThread.

chrome/browser/sessions/session_service.cc

 // Copyright (c) 2011 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.
 
 #include "chrome/browser/sessions/session_service.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <vector>
@@ skipping 164 matching lines @@
   ScheduleReset();
 }
 
 void SessionService::MoveCurrentSessionToLastSession() {
   pending_tab_close_ids_.clear();
   window_closing_ids_.clear();
   pending_window_close_ids_.clear();
 
   Save();
 
-  if (!backend_thread()) {
-    backend()->MoveCurrentSessionToLastSession();
-  } else {
-    backend_thread()->message_loop()->PostTask(
-        FROM_HERE, base::Bind(&SessionBackend::MoveCurrentSessionToLastSession,
-                              backend()));
-  }
+  RunTaskOnBackendThread(
+      FROM_HERE, base::Bind(&SessionBackend::MoveCurrentSessionToLastSession,
+                            backend()));
 }
 
 void SessionService::SetTabWindow(const SessionID& window_id,
                                   const SessionID& tab_id) {
   if (!ShouldTrackChangesToWindow(window_id))
     return;
 
   ScheduleCommand(CreateSetTabWindowCommand(window_id, tab_id));
 }
 
@@ skipping 1336 matching lines @@
       50);
   if (use_long_period) {
     std::string long_name_("SessionRestore.SaveLongPeriod");
     UMA_HISTOGRAM_CUSTOM_TIMES(long_name_,
         delta,
         save_delay_in_mins_,
         save_delay_in_hrs_,
         50);
   }
 }