change a stringstream over to stringbuilder

Bug: webrtc:8982
Change-Id: I4d8605acd59926a5873bfc7ca4ce902854f2708e
Reviewed-on: https://webrtc-review.googlesource.com/64880
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23095}
diff --git a/modules/audio_coding/neteq/neteq.cc b/modules/audio_coding/neteq/neteq.cc
index 37e24ef..db12589 100644
--- a/modules/audio_coding/neteq/neteq.cc
+++ b/modules/audio_coding/neteq/neteq.cc
@@ -11,9 +11,9 @@
 #include "modules/audio_coding/neteq/include/neteq.h"
 
 #include <memory>
-#include <sstream>
 
 #include "modules/audio_coding/neteq/neteq_impl.h"
+#include "rtc_base/strings/string_builder.h"
 
 namespace webrtc {
 
@@ -25,7 +25,8 @@
 NetEq::Config& NetEq::Config::operator=(Config&&) = default;
 
 std::string NetEq::Config::ToString() const {
-  std::stringstream ss;
+  char buf[1024];
+  rtc::SimpleStringBuilder ss(buf);
   ss << "sample_rate_hz=" << sample_rate_hz
      << ", enable_post_decode_vad="
      << (enable_post_decode_vad ? "true" : "false")