Remove all remaining non-test uses of std::stringstream.

Bug: webrtc:8982
Change-Id: I635a8545c46dc8c89663d64af351e22e65cbcb33
Reviewed-on: https://webrtc-review.googlesource.com/98880
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24715}
diff --git a/modules/audio_processing/test/test_utils.h b/modules/audio_processing/test/test_utils.h
index 6e4154a..10877f1 100644
--- a/modules/audio_processing/test/test_utils.h
+++ b/modules/audio_processing/test/test_utils.h
@@ -15,6 +15,7 @@
 #include <iterator>
 #include <limits>
 #include <memory>
+#include <sstream>  // no-presubmit-check TODO(webrtc:8982)
 #include <string>
 #include <vector>