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/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 009671c..8a65e30 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -689,6 +689,9 @@
     "json.cc",
     "json.h",
   ]
+  deps = [
+    ":stringutils",
+  ]
   all_dependent_configs = [ "//third_party/jsoncpp:jsoncpp_config" ]
   if (rtc_build_json) {
     public_deps = [