Android: Replace webrtc_jni namespace with nested jni namespace

webrtc/sdk/android/src/jni/pc/mediaconstraints_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/sdk/android/src/jni/pc/mediaconstraints_jni.h"
 
-namespace webrtc_jni {
+namespace webrtc {
+namespace jni {
 
 MediaConstraintsJni::MediaConstraintsJni(JNIEnv* jni, jobject j_constraints) {
   PopulateConstraintsFromJavaPairList(jni, j_constraints, "mandatory",
                                       &mandatory_);
   PopulateConstraintsFromJavaPairList(jni, j_constraints, "optional",
                                       &optional_);
 }
 
 // static
 void MediaConstraintsJni::PopulateConstraintsFromJavaPairList(
@@ skipping 13 matching lines @@
     jmethodID get_value = GetMethodID(jni, GetObjectClass(jni, entry),
                                       "getValue", "()Ljava/lang/String;");
     jstring j_value =
         reinterpret_cast<jstring>(jni->CallObjectMethod(entry, get_value));
     CHECK_EXCEPTION(jni) << "error during CallObjectMethod";
     field->push_back(
         Constraint(JavaToStdString(jni, j_key), JavaToStdString(jni, j_value)));
   }
 }
 
-}  // namespace webrtc_jni
+}  // namespace jni
+}  // namespace webrtc