Add the "file_handlers" manifest key for platform apps to replace "intents".

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.
 
 {
   "app": {
     "channel": "stable",
     "extension_types": ["packaged_app", "hosted_app", "platform_app"]
   },
   // The default platform app CSP can only be overridden by whitelisted apps.
@@ skipping 101 matching lines @@
   },
   "display_in_launcher": {
     "channel": "stable",
     "extension_types": ["packaged_app", "platform_app"],
     "location": "component"
   },
   "file_browser_handlers": {
     "channel": "stable",
     "extension_types": ["extension", "packaged_app"]
   },
+  "file_handlers": {
+    "channel": "stable",
+    "extension_types": ["platform_app"]
+  },
   "homepage_url": {
     "channel": "stable",
     "extension_types": ["extension", "packaged_app"]
   },
   "icons": {
     "channel": "stable",
     "extension_types": "all"
   },
   "incognito": {
     "channel": "stable",
@@ skipping 117 matching lines @@
     "channel": "stable",
     "extension_types": "all"
   },
   "web_accessible_resources": {
     "channel": "stable",
     "extension_types": [
       "extension", "packaged_app", "hosted_app"
     ]
   }
 }