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

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

Index: webrtc/sdk/android/src/jni/peerconnection_jni.cc
diff --git a/webrtc/sdk/android/src/jni/peerconnection_jni.cc b/webrtc/sdk/android/src/jni/peerconnection_jni.cc
index 75b1bad20256dcafd288b6a953d8e686c8a216ca..3b39e62f4b647652bb0c78535cf0a09b0bca232d 100644
--- a/webrtc/sdk/android/src/jni/peerconnection_jni.cc
+++ b/webrtc/sdk/android/src/jni/peerconnection_jni.cc
@@ -1199,6 +1199,25 @@ JOW(void, PeerConnectionFactory_shutdownInternalTracer)(JNIEnv* jni, jclass) {
   rtc::tracing::ShutdownInternalTracer();
 }
 
+JOW(void, AudioSource_nativeSetVolume)
+(JNIEnv*, jclass, jlong j_p, jdouble volume) {
+  reinterpret_cast<AudioSourceInterface*>(j_p)->SetVolume(volume);
+}
+
+JOW(jobject, AudioTrack_nativeGetSource)(JNIEnv* jni, jclass, jlong j_p) {
+  rtc::scoped_refptr<AudioSourceInterface> source(
+      reinterpret_cast<AudioTrackInterface*>(j_p)->GetSource());
+
+  jlong nativePointer = jlongFromPointer(source.get());
+  jclass j_audio_source_class = FindClass(jni, "org/webrtc/AudioSource");
+  jmethodID j_audio_source_ctor =
+      GetMethodID(jni, j_audio_source_class, "<init>", "(J)V");
+  jobject j_audio_source =
+      jni->NewObject(j_audio_source_class, j_audio_source_ctor, nativePointer);
+  CHECK_EXCEPTION(jni) << "error during NewObject";
+  return j_audio_source;
+}
+
 // 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)