Convert ios_web_shell_test to GN.

ios/BUILD.gn

 # Copyright 2016 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.
 
 # This list all targets that needs to be build as part of "gn_all" on iOS.
 # This list should generally only include executables, but since some code
 # has not yet been upstreamed it will sometimes also include targets that
 # are not used upstream to ensure they are not broken inadvertently.
 group("all") {
   testonly = true
   deps = [
     "//ios/chrome:ios_chrome_unittests",
     "//ios/chrome/app",
     "//ios/chrome/browser",
     "//ios/chrome/common",
     "//ios/chrome/common/physical_web",
     "//ios/chrome/share_extension:packed_resources",
     "//ios/chrome/today_extension:packed_resources",
     "//ios/net:ios_net_unittests",
     "//ios/public/provider/chrome/browser",
     "//ios/public/provider/web",
     "//ios/testing:ocmock_support_unittest",
     "//ios/third_party/earl_grey",
     "//ios/web:ios_web_inttests",
     "//ios/web:ios_web_unittests",
     "//ios/web/shell:ios_web_shell",
+    "//ios/web/shell/test:ios_web_shell_test_host",
   ]
 
   if (!is_component_build) {
     deps += [ "//components/cronet/ios:cronet_package" ]
   }
 }