Whitelist chrome.screenlockPrivate only for component apps on ChromeOS.

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 861 matching lines @@
   "rtcPrivate": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"],
     "whitelist": [
       "53041A2FA309EECED01FFC751E7399186E860B2C",  // Google Talk prod
       "A74A4D44C7CFCD8844830E6140C8D763E12DD8F3",  // Google Talk beta
       "E7E2461CE072DF036CF9592740196159E2D7C089",  // Google Talk alpha
       "312745D9BF916161191143F6490085EEA0434997"   // Google Talk debug
     ]
   },
-  "screenlockPrivate": {
+  "screenlockPrivate": [{
+    "platforms": ["chromeos"],
+    "channel": "stable",
+    "extension_types": ["platform_app"],
+    "location": "component"
+  }, {
+    "platforms": ["mac", "win", "linux"],
     "channel": "stable",
     "extension_types": ["platform_app"],
     "whitelist": [
       "lkegkdgachcnekllcdfkijonogckdnjo",  // API test
-      "190C131D270994E7330E9A3CD48224061CB10E2D",  // dogfood 1
-      "7FDDD1C0CB0052596657FDEC92841D509DC8D404",  // dogfood 2
-      "E13990DC5440B6E270503DA27A35762F423725C3"   // dogfood 3
+      "E13990DC5440B6E270503DA27A35762F423725C3"   // dogfood
     ]
-  },
+  }],
   "screensaver": {
     "channel": "stable",
     "extension_types": ["legacy_packaged_app", "hosted_app", "platform_app"]
   },
   "serial": {
     "channel": "stable",
     "extension_types": ["platform_app"]
   },
   "sessions": {
     "channel": "stable",
@@ skipping 184 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
     ]
   }]
 }