Update GN build files for new prefs location.

ios/chrome/BUILD.gn

 # 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.
 
 import("//testing/test.gni")
 
 test("ios_chrome_unittests") {
   sources = [
     "app/safe_mode_util_unittest.cc",
     "browser/chrome_url_util_unittest.mm",
@@ skipping 24 matching lines @@
     "browser/ui/native_content_controller_unittest.mm",
     "browser/ui/ui_util_unittest.mm",
     "browser/ui/uikit_ui_util_unittest.mm",
     "browser/update_client/ios_chrome_update_query_params_delegate_unittest.cc",
     "browser/web_resource/web_resource_util_unittest.cc",
     "common/string_util_unittest.mm",
   ]
 
   deps = [
     "//base",
-    "//base:prefs_test_support",
     "//base/test:test_support",
     "//components/bookmarks/test",
     "//components/favicon_base",
     "//components/metrics",
     "//components/metrics:test_support",
+    "//components/prefs:test_support",
     "//components/signin/core/browser:test_support",
     "//components/signin/ios/browser:test_support",
     "//components/sync_driver:test_support",
     "//components/update_client",
     "//components/version_info",
     "//ios/chrome/app",
     "//ios/chrome/browser",
     "//ios/chrome/browser:test_support",
     "//ios/chrome/common",
     "//ios/public/test",
@@ skipping 20 matching lines @@
   #       'test_data_files': [
   #         'test/data/webdata/bookmarkimages',
   #       ],
   #       'test_data_prefix': 'ios/chrome',
   #     },
   #     'includes': [ '../../build/copy_test_data_ios.gypi' ]
   #   },
   # ],
   # 'includes': ['ios_chrome_resources_bundle.gypi'],
 }