title: WebRTC iOS local video track not render on RTCEAGLVideoView
body: <p>I want render local camera capturer's video track on RTCEAGLView instead of RTCCameraPreviewView before connect to room. I created a local video track as below in viewDidLoad:</p>
  
  <pre><code>    let dF = RTCDefaultVideoDecoderFactory.init()
      let eF = RTCDefaultVideoEncoderFactory.init()
      eF.preferredCodec = ARDSettingsModel.init().currentVideoCodecSettingFromStore()
      RTCPeerConnectionFactory.init()
      let factory = RTCPeerConnectionFactory.init(encoderFactory: eF, decoderFactory: dF)
      let videoSource = factory.videoSource()
      capturer = RTCCameraVideoCapturer.init(delegate: videoSource)
      capturerController = ARDCaptureController.init(capturer: capturer, settings: ARDSettingsModel.init())
      capturerController?.startCapture()
      let rtcTrack = factory.videoTrack(with: videoSource, trackId: "ARDAMSv0")
      let localView = RTCEAGLVideoView.init(frame: self.view.bounds)
      self.view.addSubview(localView)
      rtcTrack.add(localView)
  </code></pre>
  
  <p>The RTCEAGLVideoView did added as subview, but the track did not render on the view, anyone know why?</p>
  
  <p>I have success get preview view by RTCCameraPreviewView if using:</p>
  
  <pre><code>    let localView2 = RTCCameraPreviewView.init(frame: self.view.bounds)
      localView2.captureSession = capturer?.captureSession
      self.view.addSubview(localView2)
  </code></pre>