Add a new QUIC platform API for text utilities.

net/quic/core/quic_tag.cc

Index: net/quic/core/quic_tag.cc
diff --git a/net/quic/core/quic_tag.cc b/net/quic/core/quic_tag.cc
index 584f582ebb49934d2563cbd3e9f06338fc6b03af..1bb93351a7731913e2f5048cc2d7806500ad6cc8 100644
--- a/net/quic/core/quic_tag.cc
+++ b/net/quic/core/quic_tag.cc
@@ -7,7 +7,7 @@
 #include <algorithm>
 
 #include "base/macros.h"
-#include "base/strings/string_number_conversions.h"
+#include "net/quic/platform/api/quic_text_utils.h"
 
 namespace net {
 
@@ -56,7 +56,7 @@ std::string QuicTagToString(QuicTag tag) {
     return std::string(chars, sizeof(chars));
   }
 
-  return base::UintToString(orig_tag);
+  return QuicTextUtils::Uint64ToString(orig_tag);
 }
 
 uint32_t MakeQuicTag(char a, char b, char c, char d) {