[cast_channel] Make CastSocket not inherit from ApiResource

extensions/browser/api/cast_channel/BUILD.gn

 # Copyright 2016 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.
 
 source_set("cast_channel") {
   sources = [
     "cast_auth_util.cc",
     "cast_auth_util.h",
     "cast_channel_api.cc",
     "cast_channel_api.h",
     "cast_framer.cc",
     "cast_framer.h",
     "cast_message_util.cc",
     "cast_message_util.h",
     "cast_socket.cc",
     "cast_socket.h",
+    "cast_socket_service.cc",
+    "cast_socket_service.h",
+    "cast_socket_service_factory.cc",
+    "cast_socket_service_factory.h",
     "cast_transport.cc",
     "cast_transport.h",
     "keep_alive_delegate.cc",
     "keep_alive_delegate.h",
     "logger.cc",
     "logger.h",
   ]
 
   deps = [
     "//base",
     "//extensions/common/api",
     "//extensions/common/api/cast_channel:cast_channel_proto",
     "//net",
   ]
 
   public_deps = [
     "//extensions/browser:browser_sources",
   ]
 }