Remove duplicated user_prefs::TestingPrefServiceSyncable

extensions/browser/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/features.gni")
 import("//extensions/features/features.gni")
 
 source_set("browser") {
   sources = []
 
@@ skipping 412 matching lines @@
 
   deps = [
     ":browser",
     "//base",
     "//base/test:test_support",
     "//components/cast_certificate",
     "//components/cast_certificate:test_support",
     "//components/cast_certificate/proto:unittest_proto",
     "//components/crx_file",
     "//components/keyed_service/content",
-    "//components/pref_registry:test_support",
+    "//components/pref_registry:pref_registry",
     "//components/prefs:test_support",
+    "//components/sync_preferences:test_support",
     "//components/update_client",
     "//components/url_matcher",
     "//components/user_prefs",
     "//content/test:test_support",
     "//device/bluetooth:mocks",
     "//device/power_save_blocker",
     "//extensions:extensions_browser_resources",
     "//extensions:test_support",
     "//extensions/common",
     "//extensions/common/api",
     "//extensions/features",
     "//ipc:test_support",
     "//net:test_support",
     "//third_party/leveldatabase",
     "//third_party/zlib:zip",
   ]
 
   if (is_chromeos) {
     sources += [ "api/webcam_private/visca_webcam_unittest.cc" ]
     deps += [ "//chromeos:test_support" ]
   }
 }