Implement the feedbackPrivate 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.
 
 // 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 186 matching lines @@
       "inmdanhiiibfpdlljnjjbchhjgelojnn",  // Dogfood
       "cbpmgnfekbgbgpkmokfppmldaccjcbnb"   // Test
     ]
   },
   "experimental": {
     "channel": "stable",
     "extension_types": [
       "extension", "packaged_app", "hosted_app", "platform_app"
     ]
   },
+  "feedbackPrivate": {
+    "channel": "stable",
+    "extension_types": ["extension", "platform_app"],
+    "whitelist": [
+      "7910EAFDAF64B947E1CB31B333A9BD14CA556B6C" // Feedback UI.
+    ]
+  },
   "fileBrowserHandler": {
     "channel": "stable",
     "extension_types": ["extension", "packaged_app", "platform_app"]
   },
   "fileBrowserPrivate": {
     "channel": "stable",
     "extension_types": ["extension", "packaged_app"],
     "location": "component"
   },
   "fileSystem": [{
@@ skipping 404 matching lines @@
   },
   "webRequestBlocking": {
     "channel": "stable",
     "extension_types": ["extension", "packaged_app"]
   },
   "webview": {
     "channel": "stable",
     "extension_types": ["platform_app"]
   }
 }