Relanding: Break peerconnection_jni.cc into multiple files, in "pc" directory.

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

Index: webrtc/sdk/android/src/jni/pc/audiotrack_jni.cc
diff --git a/webrtc/sdk/android/src/jni/null_audio_jni.cc b/webrtc/sdk/android/src/jni/pc/audiotrack_jni.cc
similarity index 57%
copy from webrtc/sdk/android/src/jni/null_audio_jni.cc
copy to webrtc/sdk/android/src/jni/pc/audiotrack_jni.cc
index f9870cac049434effe7e2bcbafc793a026ad8146..dbe64f0791289b3ff380c9d8a1678e262c8aaf57 100644
--- a/webrtc/sdk/android/src/jni/null_audio_jni.cc
+++ b/webrtc/sdk/android/src/jni/pc/audiotrack_jni.cc
@@ -7,16 +7,17 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
-#include "webrtc/sdk/android/src/jni/audio_jni.h"
 
-namespace webrtc_jni {
+#include "webrtc/api/mediastreaminterface.h"
+#include "webrtc/sdk/android/src/jni/jni_helpers.h"
 
-rtc::scoped_refptr<webrtc::AudioDecoderFactory> CreateAudioDecoderFactory() {
-  return nullptr;
-}
+namespace webrtc_jni {
 
-rtc::scoped_refptr<webrtc::AudioEncoderFactory> CreateAudioEncoderFactory() {
-  return nullptr;
+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