Android: Replace webrtc_jni namespace with nested jni namespace

webrtc/sdk/android/src/jni/wrapped_native_i420_buffer.h

 /*
  *  Copyright (c) 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.
  */
 
 #ifndef WEBRTC_SDK_ANDROID_SRC_JNI_WRAPPED_NATIVE_I420_BUFFER_H_
 #define WEBRTC_SDK_ANDROID_SRC_JNI_WRAPPED_NATIVE_I420_BUFFER_H_
 
 #include <jni.h>
 
 #include "webrtc/api/video/video_frame_buffer.h"
 
-namespace webrtc_jni {
+namespace webrtc {
+namespace jni {
 
 // This function wraps the C++ I420 buffer and returns a Java
 // VideoFrame.I420Buffer as a jobject.
 jobject WrapI420Buffer(
     JNIEnv* jni,
-    const rtc::scoped_refptr<webrtc::I420BufferInterface>& i420_buffer);
+    const rtc::scoped_refptr<I420BufferInterface>& i420_buffer);
 
-}  // namespace webrtc_jni
+}  // namespace jni
+}  // namespace webrtc
 
 #endif  // WEBRTC_SDK_ANDROID_SRC_JNI_WRAPPED_NATIVE_I420_BUFFER_H_