Add a new QUIC platform API for text utilities.

net/quic/core/quic_crypto_server_stream.cc

Index: net/quic/core/quic_crypto_server_stream.cc
diff --git a/net/quic/core/quic_crypto_server_stream.cc b/net/quic/core/quic_crypto_server_stream.cc
index f1b604141e575e7c9585eba87f7d31a879916da0..641f034ee2ec4eec8389d6699d52792504b31c66 100644
--- a/net/quic/core/quic_crypto_server_stream.cc
+++ b/net/quic/core/quic_crypto_server_stream.cc
@@ -17,6 +17,7 @@
 #include "net/quic/core/quic_flags.h"
 #include "net/quic/core/quic_packets.h"
 #include "net/quic/core/quic_session.h"
+#include "net/quic/platform/api/quic_text_utils.h"
 
 using base::StringPiece;
 using std::string;
@@ -421,19 +422,7 @@ bool QuicCryptoServerStream::GetBase64SHA256ClientChannelID(
   uint8_t digest[32];
   hash->Finish(digest, sizeof(digest));
 
-  base::Base64Encode(
-      string(reinterpret_cast<const char*>(digest), sizeof(digest)), output);
-  // Remove padding.
-  size_t len = output->size();
-  if (len >= 2) {
-    if ((*output)[len - 1] == '=') {
-      len--;
-      if ((*output)[len - 1] == '=') {
-        len--;
-      }
-      output->resize(len);

[Jana, 2016/12/27 23:52:48]

Why's this resize not required anymore?

[Ryan Hamilton, 2016/12/28 01:48:38]

All of this logic has moved into the new QuicTextUtils::Base64Encode method
(including the code to strip the padding)

-    }
-  }
+  QuicTextUtils::Base64Encode(digest, arraysize(digest), output);
   return true;
 }