MediaPerceptionPrivate API impl and testing.

extensions/browser/api/media_perception_private/BUILD.gn

 # 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.
 
 import("//third_party/protobuf/proto_library.gni")
 
 source_set("media_perception_private") {
   sources = [
+    "media_perception_api_manager.cc",
+    "media_perception_api_manager.h",
     "media_perception_private_api.cc",
     "media_perception_private_api.h",
   ]
 
   deps = [
     "//base",
     "//chromeos:media_perception_proto",
     "//extensions/common/api",
   ]
 }