[MD Extensions] Include the manifest code snippet in load errors

chrome/browser/resources/md_extensions/compiled_resources2.gyp

 # 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.
 {
   'targets': [
     {
       'target_name': 'animation_helper',
       'dependencies': [
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:assert',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:cr',
@@ skipping 99 matching lines @@
         '<(EXTERNS_GYP):developer_private',
         'animation_helper',
       ],
       'includes': ['../../../../third_party/closure_compiler/compile_js2.gypi'],
     },
     {
       'target_name': 'load_error',
       'dependencies': [
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:assert',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:cr',
+        '<(EXTERNS_GYP):developer_private',
       ],
       'includes': ['../../../../third_party/closure_compiler/compile_js2.gypi'],
     },
     {
       'target_name': 'manager',
       'dependencies': [
         '<(DEPTH)/ui/webui/resources/cr_elements/cr_drawer/compiled_resources2.gyp:cr_drawer',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:assert',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:cr',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:i18n_behavior',
@@ skipping 66 matching lines @@
       'target_name': 'toolbar',
       'dependencies': [
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:assert',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:cr',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:i18n_behavior',
       ],
       'includes': ['../../../../third_party/closure_compiler/compile_js2.gypi'],
     },
   ]
 }