[Chromedriver] Remove obsolete AddCookieScript.

chrome/test/chromedriver/BUILD.gn

 # Copyright 2015 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/ui.gni")
 import("//testing/test.gni")
 
 action("embed_js_in_cpp") {
   script = "embed_js_in_cpp.py"
 
   js_files = [
-    "js/add_cookie.js",
     "js/call_function.js",
     "js/execute_async_script.js",
     "js/focus.js",
     "js/get_element_region.js",
     "js/is_option_element_toggleable.js",
   ]
 
   inputs = [ "cpp_source.py" ] + js_files
 
   outputs = [
@@ skipping 380 matching lines @@
     "//base",
     "//base/test:run_all_unittests",
     "//net",
     "//net:http_server",
     "//net:test_support",
     "//testing/gtest",
     "//ui/events:test_support",
     "//url",
   ]
 }