Automated IWYU fix for TaskRunner includes.

chrome/browser/password_manager/password_store_proxy_mac.h

 // Copyright 2015 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_PASSWORD_MANAGER_PASSWORD_STORE_PROXY_MAC_H_
 #define CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_STORE_PROXY_MAC_H_
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
+#include "base/single_thread_task_runner.h"
 #include "base/threading/thread.h"
 #include "components/password_manager/core/browser/keychain_migration_status_mac.h"
 #include "components/password_manager/core/browser/password_store.h"
 #include "components/password_manager/core/common/password_manager_pref_names.h"
 #include "components/prefs/pref_member.h"
 
 namespace crypto {
 class AppleKeychain;
 }
 
@@ skipping 105 matching lines @@
   // them. If this is the case then Shutdown() flushes the tasks after stopping
   // the background thread.
   // After InitOnBackgroundThread is run once, the queue may not be modified on
   // the background thread any more.
   std::vector<base::Closure> pending_ui_tasks_;
 
   DISALLOW_COPY_AND_ASSIGN(PasswordStoreProxyMac);
 };
 
 #endif  // CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_STORE_PROXY_MAC_H_