Add a webrtc{en,de}coderfactory implementation for VideoToolbox

webrtc/sdk/objc/Framework/Classes/RTCPeerConnectionFactory.mm

Index: webrtc/sdk/objc/Framework/Classes/RTCPeerConnectionFactory.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnectionFactory.mm b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnectionFactory.mm
index 9f24aec11daf611a1a90825d50b772f2580ef552..b4764e3242219796ab21167a97629b1ef8eaf560 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCPeerConnectionFactory.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCPeerConnectionFactory.mm
@@ -21,6 +21,8 @@
 #import "RTCVideoTrack+Private.h"
 #import "WebRTC/RTCLogging.h"
 
+#include "videotoolboxvideocodecfactory.h"
+
 @implementation RTCPeerConnectionFactory {
   std::unique_ptr<rtc::Thread> _networkThread;
   std::unique_ptr<rtc::Thread> _workerThread;
@@ -44,9 +46,12 @@
     result = _signalingThread->Start();
     NSAssert(result, @"Failed to start signaling thread.");
 
+    const auto encoder_factory = new webrtc::VideoToolboxVideoEncoderFactory();

[magjed_webrtc, 2016/11/01 14:00:20]

nit: Maybe this would be slightly more clear:

std::unique_ptr<cricket::WebRtcVideoEncoderFactory> encoder_factory(
    new webrtc::VideoToolboxVideoEncoderFactory());
...
encoder_factory.release()

but I don't feel strongly about it.

[kthelgason, 2016/11/01 15:14:30]

I think that's a lot of typing to no specific purpose, but I understand what you
mean. I added a comment clarifying the transfer of ownership, but I can do this
as well if you want.

+    const auto decoder_factory = new webrtc::VideoToolboxVideoDecoderFactory();
+
     _nativeFactory = webrtc::CreatePeerConnectionFactory(
         _networkThread.get(), _workerThread.get(), _signalingThread.get(),
-        nullptr, nullptr, nullptr);
+        nullptr, encoder_factory, decoder_factory);
     NSAssert(_nativeFactory, @"Failed to initialize PeerConnectionFactory!");
   }
   return self;