Implement timing frames.

webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.mm

Index: webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.mm b/webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.mm
index 8ff27f8d3ac22c20de9e24cf10077ac6b471371a..a1c128ec48ec5cc9ee9d9be7aaa73d5f72dab000 100644
--- a/webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.mm
+++ b/webrtc/sdk/objc/Framework/Classes/VideoToolbox/encoder.mm
@@ -722,9 +722,9 @@ void H264VideoToolboxEncoder::OnEncodedFrame(
   frame.capture_time_ms_ = render_time_ms;
   frame._timeStamp = timestamp;
   frame.rotation_ = rotation;
-
   frame.content_type_ =
       (mode_ == kScreensharing) ? VideoContentType::SCREENSHARE : VideoContentType::UNSPECIFIED;
+  frame.timing_.is_timing_frame = false;
 
   h264_bitstream_parser_.ParseBitstream(buffer->data(), buffer->size());
   h264_bitstream_parser_.GetLastSliceQp(&frame.qp_);