Revert "Start the migration of passwords from the Keychain."

chrome/browser/password_manager/simple_password_store_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_SIMPLE_PASSWORD_STORE_MAC_H_
 #define CHROME_BROWSER_PASSWORD_MANAGER_SIMPLE_PASSWORD_STORE_MAC_H_
 
 #include "components/password_manager/core/browser/password_store_default.h"
 
 // The same as PasswordStoreDefault but running on the dedicated thread. The
 // owner is responsible for the thread lifetime.
 class SimplePasswordStoreMac : public password_manager::PasswordStoreDefault {
  public:
-  // Passes the arguments to PasswordStoreDefault. |background_task_runner| and
-  // |login_db| can be overwritten later in InitWithTaskRunner().
   SimplePasswordStoreMac(
       scoped_refptr<base::SingleThreadTaskRunner> main_thread_runner,
       scoped_refptr<base::SingleThreadTaskRunner> background_thread_runner,
       scoped_ptr<password_manager::LoginDatabase> login_db);
 
-  // Sets the background thread and LoginDatabase. |login_db| should be already
-  // inited. The method isn't necessary to call if the constructor already got
-  // the correct parameters.
-  void InitWithTaskRunner(
-      scoped_refptr<base::SingleThreadTaskRunner> background_task_runner,
-      scoped_ptr<password_manager::LoginDatabase> login_db);
+  // Just hides the parent method. All the initialization is to be done by
+  // PasswordStoreProxyMac that is an owner of the class.
+  bool Init(const syncer::SyncableService::StartSyncFlare& flare) override;
+
+  // Clean |background_thread_runner_|.
+  void Shutdown() override;
 
   using PasswordStoreDefault::GetBackgroundTaskRunner;
 
  protected:
   ~SimplePasswordStoreMac() override;
 
  private:
-  bool Init(const syncer::SyncableService::StartSyncFlare& flare) override;
-
   DISALLOW_COPY_AND_ASSIGN(SimplePasswordStoreMac);
 };
 
 #endif  // CHROME_BROWSER_PASSWORD_MANAGER_SIMPLE_PASSWORD_STORE_MAC_H_