Update GN build files for new prefs location.

components/keyed_service/core/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.
 
 component("core") {
   output_name = "keyed_service_core"
   sources = [
     "dependency_graph.cc",
     "dependency_graph.h",
     "dependency_manager.cc",
@@ skipping 13 matching lines @@
     "refcounted_keyed_service_factory.cc",
     "refcounted_keyed_service_factory.h",
   ]
 
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   defines = [ "KEYED_SERVICE_IMPLEMENTATION" ]
 
   deps = [
     "//base",
-    "//base:prefs",
     "//components/pref_registry",
+    "//components/prefs",
     "//components/user_prefs",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "dependency_graph_unittest.cc",
   ]
   deps = [
     ":core",
     "//base",
     "//testing/gtest",
     "//third_party/re2",
   ]
 }