Add a content_resources target which currently includes the sandbox definitions on mac

tools/gritsettings/resource_ids

 # Copyright (c) 2011 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 154 matching lines @@
   "chrome/browser/resources/workers_resources.grd": {
     "includes": [23500],
   },
   # All standard and large theme resources should have the same IDs.
   "ui/resources/ui_resources_standard.grd": {
     "includes": [24000],
   },
   "ui/resources/ui_resources_large.grd": {
     "includes": [24000],
   },
+  "content/content_resources.grd": {
+    "includes": [24500],
+  },
 }