Added support for changing the volume of AudioTrack as discussed in BUG=webrtc:6533

webrtc/sdk/android/src/jni/peerconnection_jni.cc

 /*
  *  Copyright 2013 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.
  */
 
@@ skipping 1181 matching lines @@
 
 JOW(void, PeerConnectionFactory_stopInternalTracingCapture)(
     JNIEnv* jni, jclass) {
   rtc::tracing::StopInternalCapture();
 }
 
 JOW(void, PeerConnectionFactory_shutdownInternalTracer)(JNIEnv* jni, jclass) {
   rtc::tracing::ShutdownInternalTracer();
 }
 
+JOW(void, AudioTrack_nativeSetVolume)
+(JNIEnv*, jclass, jlong j_p, jdouble volume) {
+  rtc::scoped_refptr<AudioSourceInterface> source(
+      reinterpret_cast<AudioTrackInterface*>(j_p)->GetSource());
+
+  jlong nativePointer = jlongFromPointer(source.get());

[magjed_webrtc, 2017/04/05 19:14:00]

It looks like you are converting AudioSourceInterface to jlong and then back to
AudioSourceInterface again. Can't you just replace the last two lines with:
source->SetVolume(volume);
?

+
+  reinterpret_cast<AudioSourceInterface*>(nativePointer)->SetVolume(volume);
+}
+
 // Helper struct for working around the fact that CreatePeerConnectionFactory()
 // comes in two flavors: either entirely automagical (constructing its own
 // threads and deleting them on teardown, but no external codec factory support)
 // or entirely manual (requires caller to delete threads after factory
 // teardown).  This struct takes ownership of its ctor's arguments to present a
 // single thing for Java to hold and eventually free.
 class OwnedFactoryAndThreads {
  public:
   OwnedFactoryAndThreads(std::unique_ptr<Thread> network_thread,
                          std::unique_ptr<Thread> worker_thread,
@@ skipping 1515 matching lines @@
   return reinterpret_cast<DtmfSenderInterface*>(j_dtmf_sender_pointer)
       ->inter_tone_gap();
 }
 
 JOW(void, DtmfSender_free)
 (JNIEnv* jni, jclass, jlong j_dtmf_sender_pointer) {
   reinterpret_cast<DtmfSenderInterface*>(j_dtmf_sender_pointer)->Release();
 }
 
 }  // namespace webrtc_jni