[Extensions] Remove principalsPrivate 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 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 789 matching lines @@
         "3F65507A3B39259B38C8173C6FFA3D12DF64CCE9",  // http://crbug.com/371562
         "852290F2442EEE45EF673B8DA6090112079012A2"   // http://crbug.com/375484
       ]
     },
     {
       "channel": "stable",
       "extension_types": ["platform_app"],
       "location": "component"
     }
   ],
-  "principalsPrivate": {
-    "channel": "stable",
-    "extension_types": ["extension"],
-    "whitelist": [
-      "2779FA8B45841D61A37207CCFAC9CB393964FE5B"  // Login Proxy (prototype)
-    ]
-  },
   "privacy": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "processes": [{
     "channel": "dev",
     "extension_types": ["extension"]
   }, {
     "channel": "beta",
     "extension_types": ["extension"],
@@ skipping 222 matching lines @@
     "channel": "stable",
     "extension_types": ["platform_app"],
     "platforms": ["chromeos"],
     "whitelist": [
       "A948368FC53BE437A55FEB414106E207925482F5",  // Files app
       "8C726564C6DBE7380BAB388DE6CC7EC93EB44B06",  // Video player
       "5065C83E84321221675D20FBE4DC43C655CC8C6F"   // Files app tests
     ]
   }
 }