message: Speed up per frame debug log in vp9 encoder wrapper
  For the linked test case that speeds up chromium fuzzer by ~13%
  Run time decrease from ~50 seconds to ~44 seconds
  Cr-Commit-Position: refs/heads/main@{#38038}
diff: @@ -1462,7 +1462,9 @@ void LibvpxVp9Encoder::FillReferenceIndices(const vpx_codec_cx_pkt& pkt,
  vpx_svc_ref_frame_config_t enc_layer_conf = {{0}};
  libvpx_->codec_control(encoder_, VP9E_GET_SVC_REF_FRAME_CONFIG,
  &enc_layer_conf);
  - int ref_buf_flags = 0;
  + char ref_buf_flags[] = "00000000";
  + // There should be one character per buffer + 1 termination '\0'.
  + static_assert(sizeof(ref_buf_flags) == kNumVp9Buffers + 1);
  if (enc_layer_conf.reference_last[layer_id.spatial_layer_id]) {
  const size_t fb_idx =
  @@ -1471,7 +1473,7 @@ void LibvpxVp9Encoder::FillReferenceIndices(const vpx_codec_cx_pkt& pkt,
  if (std::find(ref_buf_list.begin(), ref_buf_list.end(),
  ref_buf_[fb_idx]) == ref_buf_list.end()) {
  ref_buf_list.push_back(ref_buf_[fb_idx]);
  - ref_buf_flags |= 1 << fb_idx;
  + ref_buf_flags[fb_idx] = '1';
  }
  }
  @@ -1482,7 +1484,7 @@ void LibvpxVp9Encoder::FillReferenceIndices(const vpx_codec_cx_pkt& pkt,
  if (std::find(ref_buf_list.begin(), ref_buf_list.end(),
  ref_buf_[fb_idx]) == ref_buf_list.end()) {
  ref_buf_list.push_back(ref_buf_[fb_idx]);
  - ref_buf_flags |= 1 << fb_idx;
  + ref_buf_flags[fb_idx] = '1';
  }
  }
  @@ -1493,21 +1495,14 @@ void LibvpxVp9Encoder::FillReferenceIndices(const vpx_codec_cx_pkt& pkt,
  if (std::find(ref_buf_list.begin(), ref_buf_list.end(),
  ref_buf_[fb_idx]) == ref_buf_list.end()) {
  ref_buf_list.push_back(ref_buf_[fb_idx]);
  - ref_buf_flags |= 1 << fb_idx;
  + ref_buf_flags[fb_idx] = '1';
  }
  }
  RTC_LOG(LS_VERBOSE) << "Frame " << pic_num << " sl "
  << layer_id.spatial_layer_id << " tl "
  << layer_id.temporal_layer_id << " refered buffers "
  - << (ref_buf_flags & (1 << 0) ? 1 : 0)
  - << (ref_buf_flags & (1 << 1) ? 1 : 0)
  - << (ref_buf_flags & (1 << 2) ? 1 : 0)
  - << (ref_buf_flags & (1 << 3) ? 1 : 0)
  - << (ref_buf_flags & (1 << 4) ? 1 : 0)
  - << (ref_buf_flags & (1 << 5) ? 1 : 0)
  - << (ref_buf_flags & (1 << 6) ? 1 : 0)
  - << (ref_buf_flags & (1 << 7) ? 1 : 0);
  + << ref_buf_flags;
  } else if (!is_key_frame) {
  RTC_DCHECK_EQ(num_spatial_layers_, 1);
  