Media Galleries: Disable write support.

chrome/common/extensions/api/_permission_features.json

 // 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.
 
 {
   "activeTab": {
     "channel": "stable",
     "extension_types": ["extension", "packaged_app"],
     "min_manifest_version": 2
   },
@@ skipping 206 matching lines @@
     "extension_types": [ "platform_app" ]
   },
   "mediaGalleries.allAutoDetected": {
     "channel": "stable",
     "extension_types": [ "platform_app" ]
   },
   "mediaGalleries.read": {
     "channel": "stable",
     "extension_types": [ "platform_app" ]
   },
-  "mediaGalleries.write": {
-    "channel": "stable",
-    "extension_types": [ "platform_app" ]
-  },
   // TODO(thestig) Remove this as part of http:://crbug.com/144496
   "mediaGalleriesPrivate": {
     "channel": "stable",
     "extension_types": [ "platform_app" ],
     "whitelist": [
       "ebpbnabdhheoknfklmpddcdijjkmklkp",
       "efjnaogkjbogokcnohkmnjdojkikgobo",
       "ejegoaikibpmikoejfephaneibodccma"
     ]
   },
@@ skipping 198 matching lines @@
   },
   "webRequestBlocking": {
     "channel": "stable",
     "extension_types": ["extension", "packaged_app"]
   },
   "webview": {
     "channel": "stable",
     "extension_types": ["platform_app"]
   }
 }