Take chrome.sessions API to 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 839 matching lines @@
   },
   "screensaver": {
     "channel": "stable",
     "extension_types": ["legacy_packaged_app", "hosted_app", "platform_app"]
   },
   "serial": {
     "channel": "stable",
     "extension_types": ["platform_app"]
   },
   "sessions": {
-    "channel": "dev",
+    "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "signedInDevices": {
     "channel": "dev",
     "extension_types": ["extension", "legacy_packaged_app", "platform_app"]
   },
   "streamsPrivate": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app", "platform_app"],
     "whitelist": [
@@ skipping 170 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
     ]
   }]
 }