This CL removes all usages of our custom ostream << overloads.

This prepares us for removing them altogether.

Bug: webrtc:8982
Change-Id: I66002cc8d4bf0e07925766d568d2498422f0f38e
Reviewed-on: https://webrtc-review.googlesource.com/64142
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Reviewed-by: Henrik Grunell <henrikg@webrtc.org>
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22707}
diff --git a/rtc_base/stringutils.h b/rtc_base/stringutils.h
index 386ca9e..b42cfa5 100644
--- a/rtc_base/stringutils.h
+++ b/rtc_base/stringutils.h
@@ -312,6 +312,7 @@
 // Remove leading and trailing whitespaces.
 std::string string_trim(const std::string& s);
 
+// TODO(jonasolsson): replace with absl::Hex when that becomes available.
 std::string ToHex(const int i);
 }  // namespace rtc