Android: Replace webrtc_jni namespace with nested jni namespace

webrtc/sdk/android/src/jni/pc/mediasource_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(jobject,
                          MediaSource_nativeState,
                          JNIEnv* jni,
                          jclass,
                          jlong j_p) {
-  rtc::scoped_refptr<webrtc::MediaSourceInterface> p(
-      reinterpret_cast<webrtc::MediaSourceInterface*>(j_p));
+  rtc::scoped_refptr<MediaSourceInterface> p(
+      reinterpret_cast<MediaSourceInterface*>(j_p));
   return JavaEnumFromIndexAndClassName(jni, "MediaSource$State", p->state());
 }
 
-}  // namespace webrtc_jni
+}  // namespace jni
+}  // namespace webrtc