Reimplement the builtin audio codec factories using the new stuff in api/

webrtc/modules/audio_coding/codecs/builtin_audio_encoder_factory_internal.h

-/*
- *  Copyright (c) 2017 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.
- */
-
-#ifndef WEBRTC_MODULES_AUDIO_CODING_CODECS_BUILTIN_AUDIO_ENCODER_FACTORY_INTERNAL_H_
-#define WEBRTC_MODULES_AUDIO_CODING_CODECS_BUILTIN_AUDIO_ENCODER_FACTORY_INTERNAL_H_
-
-#include "webrtc/api/audio_codecs/audio_encoder_factory.h"
-#include "webrtc/rtc_base/scoped_ref_ptr.h"
-
-namespace webrtc {
-
-// Creates a new factory that can create the built-in types of audio encoders.
-// NOTE: This function is still under development and may change without notice.
-rtc::scoped_refptr<AudioEncoderFactory>
-CreateBuiltinAudioEncoderFactoryInternal();
-
-}  // namespace webrtc
-
-#endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_BUILTIN_AUDIO_ENCODER_FACTORY_INTERNAL_H_