Use content::RunBlockingPoolTask() in tests.

chrome/browser/sessions/session_service_test_helper.h

 // Copyright (c) 2012 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.
 
 #ifndef CHROME_BROWSER_SESSIONS_SESSION_SERVICE_TEST_HELPER_H_
 #define CHROME_BROWSER_SESSIONS_SESSION_SERVICE_TEST_HELPER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 37 matching lines @@
                                const SessionID& tab_id,
                                const std::string& user_agent_override);
 
   void SetForceBrowserNotAliveWithNoWindows(
       bool force_browser_not_alive_with_no_windows);
 
   // Reads the contents of the last session.
   void ReadWindows(std::vector<SessionWindow*>* windows,
                    SessionID::id_type* active_window_id);
 
-  void AssertTabEquals(SessionID& window_id,
-                       SessionID& tab_id,
+  void AssertTabEquals(const SessionID& window_id,
+                       const SessionID& tab_id,
                        int visual_index,
                        int nav_index,
                        size_t nav_count,
                        const SessionTab& session_tab);
 
   void AssertTabEquals(int visual_index,
                        int nav_index,
                        size_t nav_count,
                        const SessionTab& session_tab);
 
@@ skipping 14 matching lines @@
   void RunTaskOnBackendThread(const tracked_objects::Location& from_here,
                               const base::Closure& task);
 
  private:
   scoped_ptr<SessionService> service_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionServiceTestHelper);
 };
 
 #endif  // CHROME_BROWSER_SESSIONS_SESSION_SERVICE_TEST_HELPER_H_