Promote "chrome.browser" 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 61 matching lines @@
   },
   "bookmarks": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "brailleDisplayPrivate": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app", "platform_app"],
     "location": "component"
   },
-  "browser": [
-    {
-      "channel": "dev",
-      "extension_types": ["platform_app"]
-    },
-    {
-      "channel": "stable",
-      "extension_types": ["platform_app"],
-      "whitelist": [
-        // hotword_audio_verification
-        "B6356EFF4047BC5F868C7D91868B6F5C01951A8A"
-      ]
-    }
-  ],
+  "browser": {
+    "channel": "stable",
+    "extension_types": ["platform_app"]
+  },
   "browsingData": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "cast": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app", "platform_app"],
     "whitelist": [
       "63ED55E43214C211F82122ED56407FF1A807F2A3",  // Dev
       "FA01E0B81978950F2BC5A50512FD769725F57510",  // Beta
@@ skipping 874 matching lines @@
   "webstorePrivate": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app", "hosted_app"],
     "whitelist": [
       "B44D08FD98F1523ED5837D78D0A606EA9D6206E5",  // Web Store
       "2653F6F6C39BC6EEBD36A09AFB92A19782FF7EB4",  // Enterprise Web Store
       "2779FA8B45841D61A37207CCFAC9CB393964FE5B"   // Login Proxy (prototype)
     ]
   }
 }