MediaPerceptionPrivate API impl and testing.

extensions/test/data/media_perception_private/state/manifest.json

+// Copyright 2017 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.
+{
+  "key": "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC74Vbx3EbhPc/FOvn6+HxCjMSml0HdPMiuRjj5a3b+MnRML1iJ9OAgbKUYJ/u3s25/cGq8pNB0NbyupHGEqvqAE7TcNr1mdgs0PWxh2IOI1GKrxlzxpqzQuFmxq5WHKr5RrwZ4/Xq0t/+e8JkvhZdW0jarz/28Jom0gkM5lorsewIDAQAB",
+  "manifest_version": 2,
+  "name": "Test mediaPerceptionPrivate API's get and set state functions",
+  "version": "1.0",
+  "app": {
+    "background": {
+      "scripts": ["runtest.js"]
+    }
+  },
+  "permissions": ["mediaPerceptionPrivate"],
+  "kiosk_enabled": true,
+  "kiosk_only": true
+}