message: Update comments on Audio Level RTP header extension.
  Cr-Commit-Position: refs/heads/master@{#29666}
diff: @@ -143,7 +143,7 @@ bool AbsoluteCaptureTimeExtension::Write(rtc::ArrayView<uint8_t> data,
  // An RTP Header Extension for Client-to-Mixer Audio Level Indication
  //
  -// https://datatracker.ietf.org/doc/draft-lennox-avt-rtp-audio-level-exthdr/
  +// https://tools.ietf.org/html/rfc6464
  //
  // The form of the audio level extension block:
  //
  @@ -152,7 +152,15 @@ bool AbsoluteCaptureTimeExtension::Write(rtc::ArrayView<uint8_t> data,
  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  // | ID | len=0 |V| level |
  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  +// Sample Audio Level Encoding Using the One-Byte Header Format
  //
  +// 0 1 2
  +// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
  +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  +// | ID | len=1 |V| level |
  +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  +// Sample Audio Level Encoding Using the Two-Byte Header Format
  +
  constexpr RTPExtensionType AudioLevel::kId;
  constexpr uint8_t AudioLevel::kValueSizeBytes;
  constexpr const char AudioLevel::kUri[];
  @@ -160,6 +168,7 @@ constexpr const char AudioLevel::kUri[];
  bool AudioLevel::Parse(rtc::ArrayView<const uint8_t> data,
  bool* voice_activity,
  uint8_t* audio_level) {
  + // One-byte and two-byte format share the same data definition.
  if (data.size() != 1)
  return false;
  *voice_activity = (data[0] & 0x80) != 0;
  @@ -170,6 +179,7 @@ bool AudioLevel::Parse(rtc::ArrayView<const uint8_t> data,
  bool AudioLevel::Write(rtc::ArrayView<uint8_t> data,
  bool voice_activity,
  uint8_t audio_level) {
  + // One-byte and two-byte format share the same data definition.
  RTC_DCHECK_EQ(data.size(), 1);
  RTC_CHECK_LE(audio_level, 0x7f);
  data[0] = (voice_activity ? 0x80 : 0x00) | audio_level;
  