Remove PAC-fetching URLRequestContext.

chrome/test/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/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
@@ skipping 1438 matching lines @@
       "../browser/importer/edge_importer_browsertest_win.cc",
       "../browser/importer/firefox_importer_browsertest.cc",
       "../browser/importer/ie_importer_browsertest_win.cc",
       "../browser/importer/importer_unittest_utils.cc",
       "../browser/importer/importer_unittest_utils.h",
       "../browser/infobars/infobars_browsertest.cc",
       "../browser/installable/installable_manager_browsertest.cc",
       "../browser/interstitials/security_interstitial_page_test_utils.cc",
       "../browser/interstitials/security_interstitial_page_test_utils.h",
       "../browser/invalidation/profile_invalidation_provider_factory_browsertest.cc",
+      "../browser/io_thread_browsertest.cc",
       "../browser/lifetime/browser_close_manager_browsertest.cc",
       "../browser/loader/chrome_resource_dispatcher_host_delegate_browsertest.cc",
       "../browser/loadtimes_extension_bindings_browsertest.cc",
       "../browser/locale_tests_browsertest.cc",
       "../browser/media/defer_background_media_browsertest.cc",
       "../browser/media/encrypted_media_browsertest.cc",
       "../browser/media/encrypted_media_supported_types_browsertest.cc",
       "../browser/media/media_browsertest.cc",
       "../browser/media/media_browsertest.h",
       "../browser/media/test_license_server.cc",
@@ skipping 3666 matching lines @@
 }
 
 if (is_win) {
   loadable_module("conflicts_dll") {
     testonly = true
     sources = [
       "conflicts/conflicts_dll.cc",
     ]
   }
 }