Rollfowrad of crrev.com/2720863003/: Make --headless flag work on Mac

headless/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/chrome_build.gni")
 import("//headless/headless.gni")
 import("//build/util/process_version.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 import("//tools/grit/grit_rule.gni")
@@ skipping 267 matching lines @@
 
   deps = [
     ":gen_devtools_client_api",
     ":version_header",
     "//base",
     "//components/crash/content/browser",
     "//components/security_state/content",
     "//components/security_state/core",
     "//content/public/app:both",
     "//content/public/browser",
+    "//content/public/child:child",
     "//content/public/common",
     "//content/public/common:service_names",
     "//net",
     "//services/service_manager/public/cpp",
     "//third_party/mesa:osmesa",
     "//ui/base",
     "//ui/compositor",
     "//ui/display",
     "//ui/events/devices",
     "//url",
@@ skipping 173 matching lines @@
 
 executable("headless_example") {
   sources = [
     "app/headless_example.cc",
   ]
 
   deps = [
     "//headless:headless_shell_lib",
   ]
 }