Added an empty AudioTransportProxy to AudioState.

webrtc/audio/BUILD.gn

 # Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../build/webrtc.gni")
 
 rtc_static_library("audio") {
   sources = [
     "audio_receive_stream.cc",
     "audio_receive_stream.h",
     "audio_send_stream.cc",
     "audio_send_stream.h",
     "audio_state.cc",
     "audio_state.h",
+    "audio_transport_proxy.cc",
+    "audio_transport_proxy.h",
     "conversion.h",
     "scoped_voe_interface.h",
   ]
 
   if (!build_with_chromium && is_clang) {
     # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [
     "..:webrtc_common",
     "../api:audio_mixer_api",
     "../api:call_api",
+    "../base:rtc_base_approved",
+    "../modules/audio_device",
+    "../modules/audio_processing",
     "../system_wrappers",
     "../voice_engine",
   ]
 }
 if (rtc_include_tests) {
   rtc_source_set("audio_tests") {
     testonly = true
     sources = [
       "audio_receive_stream_unittest.cc",
       "audio_send_stream_unittest.cc",
       "audio_state_unittest.cc",
     ]
     deps = [
       ":audio",
+      "../modules/audio_device:mock_audio_device",
       "//testing/gmock",
       "//testing/gtest",
     ]
     if (!build_with_chromium && is_clang) {
       # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
   }
 }