Add the Copresence 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 295 matching lines @@
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "contextMenus": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app", "platform_app"]
   },
   "cookies": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
+  "copresence": [
+    {
+      "channel": "dev",
+      "extension_types": ["extension", "platform_app"]
+    },
+    {
+      "channel": "stable",
+      "extension_types": ["extension", "platform_app"],
+      "whitelist": [
+        "AFA728615D3A82D4017BDECEE86978543194D198",  // http://crbug.com/387999
+        "0C0426C12F94156F330FFAF346A976BA8878DE78",  // http://crbug.com/387999
+        "1C93BD3CF875F4A73C0B2A163BB8FBDA8B8B3D80",  // http://crbug.com/389230
+        "A3BC37E2148AC4E99BE4B16AF9D42DD1E592BBBE",  // http://crbug.com/389230
+        "E703483CEF33DEC18B4B6DD84B5C776FB9182BDB",  // http://crbug.com/389230
+        "307E96539209F95A1A8740C713E6998A73657D96"   // http://crbug.com/389230
+      ]
+    }
+  ],
   "copresencePrivate": {
     "channel": "stable",
     "extension_types": ["extension"],
     "location": "component",
     "whitelist": [
       "AFA728615D3A82D4017BDECEE86978543194D198"  // Whispernet Proxy
     ]
   },
   "diagnostics": [
     {
@@ skipping 806 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
     ]
   }]
 }