Add support for creating java PCF from native one.

Add support for creating java PeerConnectionFactory from native one
by adding:
1. Constructor from native pointer in java PeerConnectionFactory
2. Method NativeToJavaPeerConnectionFactory in
sdk/android/native/api/peerconnection/peerconnectionfactory.h that
provides ability to convert native factory to java one.

Bug: webrtc:8946
Change-Id: Ibe8b019bd0d45849e2b16d74663d054784526746
Reviewed-on: https://webrtc-review.googlesource.com/62344
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22564}

sdk/android/native_api/peerconnection/peerconnectionfactory.cc

@@ -0,0 +1,33 @@
+/*
+ *  Copyright 2018 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 "sdk/android/native_api/peerconnection/peerconnectionfactory.h"
+
+#include <jni.h>
+
+#include <memory>
+#include <utility>
+
+#include "sdk/android/src/jni/pc/peerconnectionfactory.h"
+
+namespace webrtc {
+
+jobject NativeToJavaPeerConnectionFactory(
+    JNIEnv* jni,
+    rtc::scoped_refptr<webrtc::PeerConnectionFactoryInterface> pcf,
+    std::unique_ptr<rtc::Thread> network_thread,
+    std::unique_ptr<rtc::Thread> worker_thread,
+    std::unique_ptr<rtc::Thread> signaling_thread,
+    rtc::NetworkMonitorFactory* network_monitor_factory) {
+  return webrtc::jni::NativeToJavaPeerConnectionFactory(
+      jni, pcf, std::move(network_thread), std::move(worker_thread),
+      std::move(signaling_thread), network_monitor_factory);
+}
+
+}  // namespace webrtc

sdk/android/native_api/peerconnection/peerconnectionfactory.h

@@ -0,0 +1,34 @@
+/*
+ *  Copyright 2018 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 SDK_ANDROID_NATIVE_API_PEERCONNECTION_PEERCONNECTIONFACTORY_H_
+#define SDK_ANDROID_NATIVE_API_PEERCONNECTION_PEERCONNECTIONFACTORY_H_
+
+#include <jni.h>
+
+#include <memory>
+
+#include "api/peerconnectioninterface.h"
+#include "rtc_base/thread.h"
+
+namespace webrtc {
+
+// Creates java PeerConnectionFactory with specified |pcf|.
+jobject NativeToJavaPeerConnectionFactory(
+    JNIEnv* jni,
+    rtc::scoped_refptr<webrtc::PeerConnectionFactoryInterface> pcf,
+    std::unique_ptr<rtc::Thread> network_thread,
+    std::unique_ptr<rtc::Thread> worker_thread,
+    std::unique_ptr<rtc::Thread> signaling_thread,
+    rtc::NetworkMonitorFactory* network_monitor_factory = nullptr);
+
+}  // namespace webrtc
+
+#endif  // SDK_ANDROID_NATIVE_API_PEERCONNECTION_PEERCONNECTIONFACTORY_H_