Whitelist experimental bookmarks extension on stable.

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 extensions/common/features/* to understand this file, in particular
 // feature.h, simple_feature.h, and base_feature_provider.h.
 
 // To add a new whitelisted ID, SHA-1 it and force it to uppercase. In Bash:
@@ skipping 690 matching lines @@
   "plugin": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "power": {
     "channel": "stable",
     "extension_types": [
       "extension", "legacy_packaged_app", "platform_app"
     ]
   },
-  "preferencesPrivate":  {
-    "channel": "dev",
+  "preferencesPrivate": {
+    "channel": "stable",
     "extension_types": [
       "extension"
     ],
     "whitelist": [
       "C41AD9DCD670210295614257EF8C9945AD68D86E",  // Google Now
       "D5736E4B5CF695CB93A2FB57E4FDC6E5AFAB6FE2",  // http://crbug.com/312900
       "D57DE394F36DC1C3220E7604C575D29C51A6C495",  // http://crbug.com/319444
       "3F65507A3B39259B38C8173C6FFA3D12DF64CCE9"   // http://crbug.com/371562
     ]
   },
@@ skipping 267 matching lines @@
     // Only allowed for whitelisted extensions until all the caveats are
     // addressed. Tracked in crbug/285151.
     "channel": "stable",
     "extension_types": ["extension"],
     "location": "component",
     "whitelist": [
       "D519188F86D9ACCEE0412007B227D9936EB9676B"  // GAIA Component Extension
     ]
   }]
 }