message: Break out sdp_serializer target
  Cr-Commit-Position: refs/heads/main@{#35880}
diff: @@ -255,8 +255,6 @@ rtc_library("peerconnection") {
  "sctp_data_channel.h",
  "sdp_offer_answer.cc", # TODO: Make separate target when not circular
  "sdp_offer_answer.h", # dependent on peerconnection.h
  - "sdp_serializer.cc",
  - "sdp_serializer.h",
  "sdp_utils.cc",
  "sdp_utils.h",
  "stats_collector.cc",
  @@ -473,6 +471,24 @@ rtc_source_set("rtc_stats_traversal") {
  }
  rtc_source_set("sdp_serializer") {
  visibility = [ ":*" ]
  + sources = [
  + "sdp_serializer.cc",
  + "sdp_serializer.h",
  + ]
  + deps = [
  + ":session_description",
  + ":simulcast_description",
  + "../api:rtc_error",
  + "../media:rtc_media_base",
  + "../modules/rtp_rtcp:rtp_rtcp_format",
  + "../rtc_base:checks",
  + "../rtc_base:stringutils",
  + ]
  + absl_deps = [
  + "//third_party/abseil-cpp/absl/algorithm:container",
  + "//third_party/abseil-cpp/absl/strings:strings",
  + "//third_party/abseil-cpp/absl/types:optional",
  + ]
  }
  rtc_source_set("sdp_utils") {
  visibility = [ ":*" ]
  @@ -1200,6 +1216,7 @@ if (rtc_include_tests && !build_with_chromium) {
  ":rtp_receiver",
  ":rtp_sender",
  ":rtp_transceiver",
  + ":sdp_serializer",
  ":session_description",
  ":usage_pattern",
  ":video_rtp_receiver",
  