Update GN build files for new prefs location.

components/wallpaper/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("wallpaper") {
   sources = [
     "wallpaper_layout.h",
     "wallpaper_resizer.cc",
     "wallpaper_resizer.h",
     "wallpaper_resizer_observer.h",
   ]
 
   defines = [ "WALLPAPER_IMPLEMENTATION" ]
 
   public_deps = [
     "//base",
     "//skia",
   ]
   deps = [
-    "//base:prefs",
+    "//components/prefs",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//url",
   ]
   if (is_chromeos) {
     sources += [
       "wallpaper_manager_base.cc",
       "wallpaper_manager_base.h",
     ]
     deps += [
       "//components/signin/core/account_id",
       "//components/user_manager",
     ]
   }
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "wallpaper_resizer_unittest.cc",
   ]
 
   deps = [
     ":wallpaper",
     "//base/test:test_support",
     "//testing/gtest",
     "//ui/gfx",
   ]
 }