Ensure tests have an active task runner

chrome/browser/background/background_contents_service_unittest.cc

 // 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.
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 44 matching lines @@
   std::string GetPrefURLForApp(Profile* profile, const base::string16& appid) {
     const base::DictionaryValue* pref = GetPrefs(profile);
     EXPECT_TRUE(pref->HasKey(base::UTF16ToUTF8(appid)));
     const base::DictionaryValue* value;
     pref->GetDictionaryWithoutPathExpansion(base::UTF16ToUTF8(appid), &value);
     std::string url;
     value->GetString("url", &url);
     return url;
   }
 
+  base::MessageLoop message_loop_;
   scoped_ptr<base::CommandLine> command_line_;
 };
 
 class MockBackgroundContents : public BackgroundContents {
  public:
   explicit MockBackgroundContents(Profile* profile)
       : appid_(base::ASCIIToUTF16("app_id")),
         profile_(profile) {
   }
   MockBackgroundContents(Profile* profile, const std::string& id)
@@ skipping 310 matching lines @@
   CreateCrashNotification(extension);
   CreateCrashNotification(extension);
 
   message_center::MessageCenter* message_center =
       message_center::MessageCenter::Get();
   message_center::NotificationList::Notifications notifications =
       message_center->GetVisibleNotifications();
   ASSERT_EQ(1u, notifications.size());
 }
 #endif