Remove duplicated user_prefs::TestingPrefServiceSyncable

chrome/test/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
@@ skipping 93 matching lines @@
     "//chrome/browser:test_support",
     "//chrome/common:test_support",
     "//chrome/renderer:test_support",
     "//components/bookmarks/test",
     "//components/gcm_driver:test_support",
     "//components/gcm_driver/instance_id:test_support",
     "//components/history/core/test:test",
     "//components/metrics:test_support",
     "//components/omnibox/browser:test_support",
     "//components/password_manager/core/browser:test_support",
-    "//components/pref_registry:test_support",
     "//components/prefs:test_support",
     "//components/rappor:test_support",
     "//components/search_engines:test_support",
     "//components/signin/core/browser:test_support",
     "//components/sync",
     "//components/sync:test_support_driver",
     "//components/sync_preferences:test_support",
     "//components/sync_sessions:test_support",
     "//components/toolbar:test_support",
     "//components/update_client:test_support",
@@ skipping 4999 matching lines @@
 }
 
 if (is_win) {
   loadable_module("conflicts_dll") {
     testonly = true
     sources = [
       "conflicts/conflicts_dll.cc",
     ]
   }
 }