Add an example app for iOS native API.

Demonstrates how to use the iOS native API to wrap components into
C++ classes.

This CL also introduces a native API wrapper for the capturer.

The C++ code is forked from the corresponding CL for Android at
https://webrtc-review.googlesource.com/c/src/+/60540

Bug: webrtc:8832
Change-Id: I12d9f30e701c0222628e329218f6d5bfca26e6e0
Reviewed-on: https://webrtc-review.googlesource.com/61422
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22484}
diff --git a/examples/objcnativeapi/objc/objccallclient.mm b/examples/objcnativeapi/objc/objccallclient.mm
new file mode 100644
index 0000000..68c58e2
--- /dev/null
+++ b/examples/objcnativeapi/objc/objccallclient.mm
@@ -0,0 +1,237 @@
+/*
+ *  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 "examples/objcnativeapi/objc/objccallclient.h"
+
+#include <utility>
+
+#import <WebRTC/RTCCameraPreviewView.h>
+#import <WebRTC/RTCVideoCodecFactory.h>
+#import <WebRTC/RTCVideoRenderer.h>
+
+#include "api/audio_codecs/builtin_audio_decoder_factory.h"
+#include "api/audio_codecs/builtin_audio_encoder_factory.h"
+#include "api/peerconnectioninterface.h"
+#include "media/engine/webrtcmediaengine.h"
+#include "modules/audio_processing/include/audio_processing.h"
+#include "rtc_base/ptr_util.h"
+#include "sdk/objc/Framework/Native/api/video_capturer.h"
+#include "sdk/objc/Framework/Native/api/video_decoder_factory.h"
+#include "sdk/objc/Framework/Native/api/video_encoder_factory.h"
+#include "sdk/objc/Framework/Native/api/video_renderer.h"
+
+namespace webrtc_examples {
+
+namespace {
+
+class CreateOfferObserver : public webrtc::CreateSessionDescriptionObserver {
+ public:
+  explicit CreateOfferObserver(rtc::scoped_refptr<webrtc::PeerConnectionInterface> pc);
+
+  void OnSuccess(webrtc::SessionDescriptionInterface* desc) override;
+  void OnFailure(const std::string& error) override;
+
+ private:
+  const rtc::scoped_refptr<webrtc::PeerConnectionInterface> pc_;
+};
+
+class SetRemoteSessionDescriptionObserver : public webrtc::SetRemoteDescriptionObserverInterface {
+ public:
+  void OnSetRemoteDescriptionComplete(webrtc::RTCError error) override;
+};
+
+class SetLocalSessionDescriptionObserver : public webrtc::SetSessionDescriptionObserver {
+ public:
+  void OnSuccess() override;
+  void OnFailure(const std::string& error) override;
+};
+
+}  // namespace
+
+ObjCCallClient::ObjCCallClient()
+    : call_started_(false), pc_observer_(rtc::MakeUnique<PCObserver>(this)) {
+  thread_checker_.DetachFromThread();
+  CreatePeerConnectionFactory();
+}
+
+void ObjCCallClient::Call(RTCVideoCapturer* capturer, id<RTCVideoRenderer> remote_renderer) {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+
+  rtc::CritScope lock(&pc_mutex_);
+  if (call_started_) {
+    RTC_LOG(LS_WARNING) << "Call already started.";
+    return;
+  }
+  call_started_ = true;
+
+  remote_sink_ = webrtc::ObjCToNativeVideoRenderer(remote_renderer);
+
+  video_source_ =
+      webrtc::ObjCToNativeVideoCapturer(capturer, signaling_thread_.get(), worker_thread_.get());
+
+  CreatePeerConnection();
+  Connect();
+}
+
+void ObjCCallClient::Hangup() {
+  RTC_DCHECK_RUN_ON(&thread_checker_);
+
+  call_started_ = false;
+
+  {
+    rtc::CritScope lock(&pc_mutex_);
+    if (pc_ != nullptr) {
+      pc_->Close();
+      pc_ = nullptr;
+    }
+  }
+
+  remote_sink_ = nullptr;
+  video_source_ = nullptr;
+}
+
+void ObjCCallClient::CreatePeerConnectionFactory() {
+  network_thread_ = rtc::Thread::CreateWithSocketServer();
+  network_thread_->SetName("network_thread", nullptr);
+  RTC_CHECK(network_thread_->Start()) << "Failed to start thread";
+
+  worker_thread_ = rtc::Thread::Create();
+  worker_thread_->SetName("worker_thread", nullptr);
+  RTC_CHECK(worker_thread_->Start()) << "Failed to start thread";
+
+  signaling_thread_ = rtc::Thread::Create();
+  signaling_thread_->SetName("signaling_thread", nullptr);
+  RTC_CHECK(signaling_thread_->Start()) << "Failed to start thread";
+
+  std::unique_ptr<webrtc::VideoDecoderFactory> videoDecoderFactory =
+      webrtc::ObjCToNativeVideoDecoderFactory([[RTCDefaultVideoDecoderFactory alloc] init]);
+  std::unique_ptr<webrtc::VideoEncoderFactory> videoEncoderFactory =
+      webrtc::ObjCToNativeVideoEncoderFactory([[RTCDefaultVideoEncoderFactory alloc] init]);
+
+  std::unique_ptr<cricket::MediaEngineInterface> media_engine =
+      cricket::WebRtcMediaEngineFactory::Create(nullptr /* adm */,
+                                                webrtc::CreateBuiltinAudioEncoderFactory(),
+                                                webrtc::CreateBuiltinAudioDecoderFactory(),
+                                                std::move(videoEncoderFactory),
+                                                std::move(videoDecoderFactory),
+                                                nullptr /* audio_mixer */,
+                                                webrtc::AudioProcessingBuilder().Create());
+  RTC_LOG(LS_INFO) << "Media engine created: " << media_engine.get();
+
+  pcf_ = webrtc::CreateModularPeerConnectionFactory(network_thread_.get(),
+                                                    worker_thread_.get(),
+                                                    signaling_thread_.get(),
+                                                    std::move(media_engine),
+                                                    webrtc::CreateCallFactory(),
+                                                    webrtc::CreateRtcEventLogFactory());
+  RTC_LOG(LS_INFO) << "PeerConnectionFactory created: " << pcf_;
+}
+
+void ObjCCallClient::CreatePeerConnection() {
+  rtc::CritScope lock(&pc_mutex_);
+  webrtc::PeerConnectionInterface::RTCConfiguration config;
+  config.sdp_semantics = webrtc::SdpSemantics::kUnifiedPlan;
+  // DTLS SRTP has to be disabled for loopback to work.
+  config.enable_dtls_srtp = false;
+  pc_ = pcf_->CreatePeerConnection(
+      config, nullptr /* port_allocator */, nullptr /* cert_generator */, pc_observer_.get());
+  RTC_LOG(LS_INFO) << "PeerConnection created: " << pc_;
+
+  rtc::scoped_refptr<webrtc::VideoTrackInterface> local_video_track =
+      pcf_->CreateVideoTrack("video", video_source_);
+  pc_->AddTransceiver(local_video_track);
+  RTC_LOG(LS_INFO) << "Local video sink set up: " << local_video_track;
+
+  for (const rtc::scoped_refptr<webrtc::RtpTransceiverInterface>& tranceiver :
+       pc_->GetTransceivers()) {
+    rtc::scoped_refptr<webrtc::MediaStreamTrackInterface> track = tranceiver->receiver()->track();
+    if (track && track->kind() == webrtc::MediaStreamTrackInterface::kVideoKind) {
+      static_cast<webrtc::VideoTrackInterface*>(track.get())
+          ->AddOrUpdateSink(remote_sink_.get(), rtc::VideoSinkWants());
+      RTC_LOG(LS_INFO) << "Remote video sink set up: " << track;
+      break;
+    }
+  }
+}
+
+void ObjCCallClient::Connect() {
+  rtc::CritScope lock(&pc_mutex_);
+  pc_->CreateOffer(new rtc::RefCountedObject<CreateOfferObserver>(pc_),
+                   webrtc::PeerConnectionInterface::RTCOfferAnswerOptions());
+}
+
+ObjCCallClient::PCObserver::PCObserver(ObjCCallClient* client) : client_(client) {}
+
+void ObjCCallClient::PCObserver::OnSignalingChange(
+    webrtc::PeerConnectionInterface::SignalingState new_state) {
+  RTC_LOG(LS_INFO) << "OnSignalingChange: " << new_state;
+}
+
+void ObjCCallClient::PCObserver::OnDataChannel(
+    rtc::scoped_refptr<webrtc::DataChannelInterface> data_channel) {
+  RTC_LOG(LS_INFO) << "OnDataChannel";
+}
+
+void ObjCCallClient::PCObserver::OnRenegotiationNeeded() {
+  RTC_LOG(LS_INFO) << "OnRenegotiationNeeded";
+}
+
+void ObjCCallClient::PCObserver::OnIceConnectionChange(
+    webrtc::PeerConnectionInterface::IceConnectionState new_state) {
+  RTC_LOG(LS_INFO) << "OnIceConnectionChange: " << new_state;
+}
+
+void ObjCCallClient::PCObserver::OnIceGatheringChange(
+    webrtc::PeerConnectionInterface::IceGatheringState new_state) {
+  RTC_LOG(LS_INFO) << "OnIceGatheringChange: " << new_state;
+}
+
+void ObjCCallClient::PCObserver::OnIceCandidate(const webrtc::IceCandidateInterface* candidate) {
+  RTC_LOG(LS_INFO) << "OnIceCandidate: " << candidate->server_url();
+  rtc::CritScope lock(&client_->pc_mutex_);
+  RTC_DCHECK(client_->pc_ != nullptr);
+  client_->pc_->AddIceCandidate(candidate);
+}
+
+CreateOfferObserver::CreateOfferObserver(rtc::scoped_refptr<webrtc::PeerConnectionInterface> pc)
+    : pc_(pc) {}
+
+void CreateOfferObserver::OnSuccess(webrtc::SessionDescriptionInterface* desc) {
+  std::string sdp;
+  desc->ToString(&sdp);
+  RTC_LOG(LS_INFO) << "Created offer: " << sdp;
+
+  // Ownership of desc was transferred to us, now we transfer it forward.
+  pc_->SetLocalDescription(new rtc::RefCountedObject<SetLocalSessionDescriptionObserver>(), desc);
+
+  // Generate a fake answer.
+  std::unique_ptr<webrtc::SessionDescriptionInterface> answer(
+      webrtc::CreateSessionDescription(webrtc::SdpType::kAnswer, sdp));
+  pc_->SetRemoteDescription(std::move(answer),
+                            new rtc::RefCountedObject<SetRemoteSessionDescriptionObserver>());
+}
+
+void CreateOfferObserver::OnFailure(const std::string& error) {
+  RTC_LOG(LS_INFO) << "Failed to create offer: " << error;
+}
+
+void SetRemoteSessionDescriptionObserver::OnSetRemoteDescriptionComplete(webrtc::RTCError error) {
+  RTC_LOG(LS_INFO) << "Set remote description: " << error.message();
+}
+
+void SetLocalSessionDescriptionObserver::OnSuccess() {
+  RTC_LOG(LS_INFO) << "Set local description success!";
+}
+
+void SetLocalSessionDescriptionObserver::OnFailure(const std::string& error) {
+  RTC_LOG(LS_INFO) << "Set local description failure: " << error;
+}
+
+}  // namespace webrtc_examples