Update I420Buffer to new VideoFrameBuffer interface

webrtc/examples/peerconnection/client/main_wnd.cc

Index: webrtc/examples/peerconnection/client/main_wnd.cc
diff --git a/webrtc/examples/peerconnection/client/main_wnd.cc b/webrtc/examples/peerconnection/client/main_wnd.cc
index a869f5b0311f7a86d477883605ee95d618f959cd..74cf6f4372bd10cc7bceadcd7bce53c9c244d0c0 100644
--- a/webrtc/examples/peerconnection/client/main_wnd.cc
+++ b/webrtc/examples/peerconnection/client/main_wnd.cc
@@ -606,8 +606,8 @@ void MainWnd::VideoRenderer::OnFrame(
   {
     AutoLock<VideoRenderer> lock(this);
 
-    rtc::scoped_refptr<webrtc::VideoFrameBuffer> buffer(
-        video_frame.video_frame_buffer());
+    rtc::scoped_refptr<webrtc::PlanarYuvBuffer> buffer(
+        video_frame.video_frame_buffer()->ToI420());
     if (video_frame.rotation() != webrtc::kVideoRotation_0) {
       buffer = webrtc::I420Buffer::Rotate(*buffer, video_frame.rotation());
     }