Introduce //components/user_prefs, use to eliminate c/b/prefs dependency in Autofill.

chrome/browser/download/download_prefs.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 "chrome/browser/download/download_prefs.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/prefs/pref_service.h"
 #include "base/string_util.h"
 #include "base/strings/string_split.h"
 #include "base/sys_string_conversions.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/download/chrome_download_manager_delegate.h"
 #include "chrome/browser/download/download_extensions.h"
 #include "chrome/browser/download/download_service.h"
 #include "chrome/browser/download/download_service_factory.h"
 #include "chrome/browser/download/download_util.h"
-#include "chrome/browser/prefs/pref_registry_syncable.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/common/pref_names.h"
+#include "components/user_prefs/pref_registry_syncable.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/download_manager.h"
 #include "content/public/browser/save_page_type.h"
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/drive/drive_file_system_util.h"
 #include "chrome/browser/chromeos/drive/drive_system_service.h"
 #endif
 
 using content::BrowserContext;
@@ skipping 166 matching lines @@
     extensions.erase(extensions.size() - 1);
 
   profile_->GetPrefs()->SetString(prefs::kDownloadExtensionsToOpen, extensions);
 }
 
 bool DownloadPrefs::AutoOpenCompareFunctor::operator()(
     const base::FilePath::StringType& a,
     const base::FilePath::StringType& b) const {
   return base::FilePath::CompareLessIgnoreCase(a, b);
 }