message: Handle longer AudioSendStream::Config strings
  Switch to using StringBuilder which suports a variable sized
  buffer.
  Cr-Commit-Position: refs/heads/master@{#33215}
diff: @@ -27,8 +27,7 @@ AudioSendStream::Config::Config(Transport* send_transport)
  AudioSendStream::Config::~Config() = default;
  std::string AudioSendStream::Config::ToString() const {
  - char buf[1024];
  - rtc::SimpleStringBuilder ss(buf);
  + rtc::StringBuilder ss;
  ss << "{rtp: " << rtp.ToString();
  ss << ", rtcp_report_interval_ms: " << rtcp_report_interval_ms;
  ss << ", send_transport: " << (send_transport ? "(Transport)" : "null");
  @@ -39,8 +38,8 @@ std::string AudioSendStream::Config::ToString() const {
  ss << ", has_dscp: " << (has_dscp ? "true" : "false");
  ss << ", send_codec_spec: "
  << (send_codec_spec ? send_codec_spec->ToString() : "<unset>");
  - ss << '}';
  - return ss.str();
  + ss << "}";
  + return ss.Release();
  }
  AudioSendStream::Config::Rtp::Rtp() = default;
  