headless: Add devtools discovery page

tools/gritsettings/resource_ids

 # Copyright (c) 2012 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 file is used to assign starting resource ids for resources and strings
 # used by Chromium.  This is done to ensure that resource ids are unique
 # across all the grd files.  If you are adding a new grd file, please add
 # a new entry to this file.
 #
 # The first entry in the file, SRCDIR, is special: It is a relative path from
@@ skipping 284 matching lines @@
   "third_party/WebKit/public/blink_resources.grd": {
     "includes": [30370],
     "structures": [30670],
   },
   "chrome/browser/resources/md_policy/policy_resources.grd": {
     "structures": [30900],
   },
   "chrome/browser/resources/settings/settings_resources.grd": {
     "structures": [30920],
   },
+  "headless/lib/resources/headless_lib_resources.grd": {
+    "includes": [30940],
+  },
 
   # Resource ids starting at 31000 are reserved for projects built on Chromium.
 }