message: In RtpFrameReferenceFinder VP8 clean not yet received before filling it
  To make it generally faster, specially in case of very large picture id gaps.
  Cr-Commit-Position: refs/heads/master@{#30438}
diff: @@ -291,6 +291,16 @@ RtpFrameReferenceFinder::FrameDecision RtpFrameReferenceFinder::ManageFrameVp8(
  if (last_picture_id_ == -1)
  last_picture_id_ = frame->id.picture_id;
  + // Clean up info about not yet received frames that are too old.
  + uint16_t old_picture_id =
  + Subtract<kPicIdLength>(frame->id.picture_id, kMaxNotYetReceivedFrames);
  + auto clean_frames_to = not_yet_received_frames_.lower_bound(old_picture_id);
  + not_yet_received_frames_.erase(not_yet_received_frames_.begin(),
  + clean_frames_to);
  + // Avoid re-adding picture ids that were just erased.
  + if (AheadOf<uint16_t, kPicIdLength>(old_picture_id, last_picture_id_)) {
  + last_picture_id_ = old_picture_id;
  + }
  // Find if there has been a gap in fully received frames and save the picture
  // id of those frames in |not_yet_received_frames_|.
  if (AheadOf<uint16_t, kPicIdLength>(frame->id.picture_id, last_picture_id_)) {
  @@ -307,13 +317,6 @@ RtpFrameReferenceFinder::FrameDecision RtpFrameReferenceFinder::ManageFrameVp8(
  auto clean_layer_info_to = layer_info_.lower_bound(old_tl0_pic_idx);
  layer_info_.erase(layer_info_.begin(), clean_layer_info_to);
  - // Clean up info about not yet received frames that are too old.
  - uint16_t old_picture_id =
  - Subtract<kPicIdLength>(frame->id.picture_id, kMaxNotYetReceivedFrames);
  - auto clean_frames_to = not_yet_received_frames_.lower_bound(old_picture_id);
  - not_yet_received_frames_.erase(not_yet_received_frames_.begin(),
  - clean_frames_to);
  -
  if (frame->frame_type() == VideoFrameType::kVideoFrameKey) {
  if (codec_header.temporalIdx != 0) {
  return kDrop;
  