Add "kiosk_only" manifest attribute for platform apps.

chrome/common/extensions/api/_manifest_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.
 
 // See c/c/e/features/* to understand this file, in particular feature.h,
 // simple_feature.h, and base_feature_provider.h.
 
 {
   "app": {
     "channel": "stable",
@@ skipping 186 matching lines @@
   "key": {
     "channel": "stable",
     "extension_types": "all"
   },
   "kiosk_enabled": {
     "channel": "stable",
     "extension_types": [
       "platform_app"
     ]
   },
+  "kiosk_only": {
+    "channel": "dev",
+    "extension_types": [
+      "platform_app"
+    ]
+  },
   "manifest_version": {
     "channel": "stable",
     "extension_types": "all"
   },
   "media_galleries_handlers": {
     "channel": "dev",
     "extension_types": ["platform_app"]
   },
   "mime_types": {
     "channel": "stable",
@@ skipping 152 matching lines @@
     "channel": "stable",
     "extension_types": "all"
   },
   "web_accessible_resources": {
     "channel": "stable",
     "extension_types": [
       "extension", "legacy_packaged_app", "hosted_app"
     ]
   }
 }