message: Add empty build target modules/video_coding:video_coding_legacy
  A followup cl will move VideoCodingModule and related code into this
  target.
  Cr-Commit-Position: refs/heads/master@{#29122}
diff: @@ -209,6 +209,10 @@ rtc_source_set("video_codec_interface") {
  ]
  }
  +rtc_source_set("video_coding_legacy") {
  + visibility = [ ":video_coding_unittests" ]
  +}
  +
  rtc_source_set("codec_globals_headers") {
  visibility = [ "*" ]
  sources = [
  