WebUI: Add externs from chrome.mimeHandlerPrivate API.

third_party/closure_compiler/externs/compiled_resources2.gyp

 # Copyright 2017 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.
 
 ########################################################
 #    NOTE: THIS FILE IS GENERATED. DO NOT EDIT IT!     #
 # Instead, run create_include_gyp.py to regenerate it. #
 ########################################################
 {
   'targets': [
@@ skipping 55 matching lines @@
     },
     {
       'target_name': 'media_player_private',
       'includes': ['../include_js.gypi'],
     },
     {
       'target_name': 'metrics_private',
       'includes': ['../include_js.gypi'],
     },
     {
+      'target_name': 'mime_handler_private',
+      'includes': ['../include_js.gypi'],
+    },
+    {
       'target_name': 'networking_private',
       'includes': ['../include_js.gypi'],
     },
     {
       'target_name': 'passwords_private',
       'includes': ['../include_js.gypi'],
     },
     {
       'target_name': 'polymer-1.0',
       'includes': ['../include_js.gypi'],
@@ skipping 17 matching lines @@
     {
       'target_name': 'users_private',
       'includes': ['../include_js.gypi'],
     },
     {
       'target_name': 'web_animations',
       'includes': ['../include_js.gypi'],
     },
   ],
 }