Make developerPrivate API available in 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.
 
 // See c/c/e/features/* to understand this file, in particular feature.h,
 // simple_feature.h, and base_feature_provider.h.
 
 {
   "activeTab": {
     "channel": "stable",
@@ skipping 157 matching lines @@
         "ganomidahfnpdchomfgdoppjmmedlhia",  // CCD Testing
         "eemlkeanncmjljgehlbplemhmdmalhdc"   // CCD Release
       ]
     }
   ],
   "debugger": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "developerPrivate": {
-    "channel": "dev",
+    "channel": "stable",
     "extension_types": ["platform_app"],
     "whitelist": [
         "ohmmkhmmmpcnpikjeljgnaoabkaalbgc", // Published Apps developer tool.
         // TODO(grv): clean up once Apps developer tool is published.
         "lphgohfeebnhcpiohjndkgbhhkoapkjc",  // Apps Developer tool.
         "gonnpeheodhmhdjiimoiheniambmdcco",  // Apps Editor old.
         // TODO(grv) : clean up once after publish.
         "cbelnpbjogfbjamhpbofhlnklecjpido"  // Apps Editor published.
     ]
   },
@@ skipping 553 matching lines @@
   },
   "webRequestBlocking": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "webview": {
     "channel": "stable",
     "extension_types": ["platform_app"]
   }
 }