Merge apps/pref* to extensions/browser/pref*

apps/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("//build/config/ui.gni")
 
 static_library("apps") {
   sources = [
     "app_lifetime_monitor.cc",
@@ skipping 14 matching lines @@
     "app_window_contents.h",
     "app_window_registry.cc",
     "app_window_registry.h",
     "browser_context_keyed_service_factories.cc",
     "browser_context_keyed_service_factories.h",
     "custom_launcher_page_contents.cc",
     "custom_launcher_page_contents.h",
     "launcher.cc",
     "launcher.h",
     "metrics_names.h",
-    "pref_names.cc",
-    "pref_names.h",
-    "prefs.cc",
-    "prefs.h",
     "saved_files_service.cc",
     "saved_files_service.h",
     "saved_files_service_factory.cc",
     "saved_files_service_factory.h",
     "switches.cc",
     "switches.h",
     "ui/apps_client.cc",
     "ui/apps_client.h",
     "ui/web_contents_sizer.h",
   ]
@@ skipping 36 matching lines @@
       "//ui/strings",
       "//ui/views",
     ]
   }
 
   if (is_win) {
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     cflags = [ "/wd4267" ]
   }
 }