message: Add dummy targets for candidate breakouts
  Cr-Commit-Position: refs/heads/main@{#35852}
diff: @@ -278,19 +278,28 @@ rtc_library("peerconnection") {
  ":audio_rtp_receiver",
  ":audio_track",
  ":connection_context",
  + ":data_channel_controller",
  + ":data_channel_utils",
  ":dtmf_sender",
  + ":ice_server_parsing",
  ":jitter_buffer_delay",
  ":media_protocol_names",
  ":media_stream",
  + ":media_stream_observer",
  + ":peer_connection_factory",
  + ":peer_connection_internal",
  ":peer_connection_message_handler",
  ":proxy",
  ":remote_audio_source",
  ":rtc_pc_base",
  + ":rtc_stats_collector",
  ":rtp_parameters_conversion",
  ":rtp_receiver",
  ":rtp_sender",
  ":rtp_transceiver",
  ":rtp_transmission_manager",
  + ":sctp_data_channel",
  + ":sdp_offer_answer",
  ":sdp_state_provider",
  ":session_description",
  ":simulcast_description",
  @@ -414,6 +423,38 @@ rtc_library("connection_context") {
  ]
  }
  +# These empty targets are the future homes of files moved out of
  +# the peerconnection target. They are broken out so that other
  +# projects and modules can add dependencies as needed.
  +# TODO(bugs.webrtc.org/13634): Fill these targets with files.
  +rtc_source_set("data_channel_controller") {
  + visibility = [ ":*" ]
  +}
  +rtc_source_set("data_channel_utils") {
  + visibility = [ "*" ] # Known to be used externally
  +}
  +rtc_source_set("sctp_data_channel") {
  + visibility = [ ":*" ]
  +}
  +rtc_source_set("ice_server_parsing") {
  + visibility = [ "*" ] # Known to be used externally
  +}
  +rtc_source_set("media_stream_observer") {
  + visibility = [ ":*" ]
  +}
  +rtc_source_set("peer_connection_factory") {
  + visibility = [ "*" ] # Known to be used externally
  +}
  +rtc_source_set("peer_connection_internal") {
  + visibility = [ ":*" ]
  +}
  +rtc_source_set("rtc_stats_collector") {
  + visibility = [ ":*" ]
  +}
  +rtc_source_set("sdp_offer_answer") {
  + visibility = [ "*" ] # Known to be used externally
  +}
  +
  rtc_library("peer_connection_message_handler") {
  sources = [
  "peer_connection_message_handler.cc",
  