Revert of Break peerconnection_jni.cc into multiple files, in "pc" directory.

webrtc/sdk/android/src/jni/pc/audiotrack_jni.cc

-/*
- *  Copyright 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.
- */
-
-#include "webrtc/api/mediastreaminterface.h"
-#include "webrtc/sdk/android/src/jni/jni_helpers.h"
-
-namespace webrtc_jni {
-
-JOW(void, AudioTrack_nativeSetVolume)
-(JNIEnv*, jclass, jlong j_p, jdouble volume) {
-  rtc::scoped_refptr<webrtc::AudioSourceInterface> source(
-      reinterpret_cast<webrtc::AudioTrackInterface*>(j_p)->GetSource());
-  source->SetVolume(volume);
-}
-
-}  // namespace webrtc_jni