Bug 1552755 - Add ToHex to stringutils.h; r=ng

This was added in commit 74395345e8d2fecd504cb687eb79deee4ef394c3, but this
only cherry picks the ToHex part of that commit.

Depends on D33336

Differential Revision: https://phabricator.services.mozilla.com/D33337

--HG--
extra : moz-landing-system : lando

media/webrtc/trunk/webrtc/rtc_base/stringutils.cc

@@ -130,4 +130,11 @@ std::string string_trim(const std::string& s) {
   return s.substr(first, last - first + 1);
 }
 
+std::string ToHex(const int i) {
+  char buffer[50];
+  snprintf(buffer, sizeof(buffer), "%x", i);
+
+  return std::string(buffer);
+}
+
 }  // namespace rtc

media/webrtc/trunk/webrtc/rtc_base/stringutils.h

@@ -311,6 +311,9 @@ bool ends_with(const char *s1, const char *s2);
 // 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
 
 #endif // RTC_BASE_STRINGUTILS_H_