Remove the notificationProvider extension API

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.
 
 // This features file defines permissions for extension APIs implemented
 // under src/chrome.
 // See chrome/common/extensions/api/_features.md to understand this file, as
 // well as feature.h, simple_feature.h, and base_feature_provider.h.
 
 // If you add a new platform_app permission please update the "stubs_app" test:
@@ skipping 627 matching lines @@
       "A6C87307BBE5886CC5F1393025000E2FE8060BF2",
       "3407516021EA3669C0EC8E65E6B9837E5A521B9C"
     ]
   },
   "nativeMessaging": {
     "channel": "stable",
     "extension_types": [
       "extension", "legacy_packaged_app", "platform_app"
     ]
   },
-  "notificationProvider": {
-    "channel": "trunk",
-    "extension_types": ["extension", "platform_app"]
-  },
   "notifications": {
     // The chrome.notifications functionality listed in notifications.idl is
     // available only to extension/platform_app types. The implementation of
     // that functionality enforces that restriction in
     // NotificationsApiFunction::IsNotificationsApiAvailable(). This is more
     // complicated than other namespaces because we are sharing the
     // notifications permission with WebKit/Blink notifications.
     "channel": "stable",
     "extension_types": [
       "extension", "legacy_packaged_app", "hosted_app", "platform_app"
@@ skipping 288 matching lines @@
     "channel": "stable",
     "extension_types": ["platform_app"],
     "platforms": ["chromeos"],
     "whitelist": [
       "A948368FC53BE437A55FEB414106E207925482F5",  // Files app
       "8C726564C6DBE7380BAB388DE6CC7EC93EB44B06",  // Video player
       "5065C83E84321221675D20FBE4DC43C655CC8C6F"   // Files app tests
     ]
   }
 }