Android: Replace webrtc_jni namespace with nested jni namespace

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 {
+namespace webrtc {
+namespace jni {
 
 JNI_FUNCTION_DECLARATION(void,
                          AudioTrack_nativeSetVolume,
                          JNIEnv*,
                          jclass,
                          jlong j_p,
                          jdouble volume) {
-  rtc::scoped_refptr<webrtc::AudioSourceInterface> source(
-      reinterpret_cast<webrtc::AudioTrackInterface*>(j_p)->GetSource());
+  rtc::scoped_refptr<AudioSourceInterface> source(
+      reinterpret_cast<AudioTrackInterface*>(j_p)->GetSource());
   source->SetVolume(volume);
 }
 
-}  // namespace webrtc_jni
+}  // namespace jni
+}  // namespace webrtc