Fix IsPrecachingAllowed() to check Sync instead of Data Saver.

components/precache/content/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.
 
 static_library("content") {
   sources = [
     "precache_manager.cc",
     "precache_manager.h",
-    "precache_manager_factory.cc",
-    "precache_manager_factory.h",
   ]
 
   configs += [ "//components/precache/core:precache_config" ]
 
   deps = [
     "//base",
     "//components/precache/core",
     "//content/public/browser",
     "//url",
   ]
 }