Replace QuicString with std::string, pass 1

This replaces QuicString with std::string in all of the "QUIC proper".  I will
delete QuicString once all code using it is gone.

gfe-relnote: n/a (no functional change)
PiperOrigin-RevId: 237872023
Change-Id: I82de62c9855516b15039734d05155917e68ff4ee
diff --git a/quic/core/crypto/cert_compressor.h b/quic/core/crypto/cert_compressor.h
index 624ac71..fd73e6e 100644
--- a/quic/core/crypto/cert_compressor.h
+++ b/quic/core/crypto/cert_compressor.h
@@ -37,19 +37,19 @@
   // sets known locally and |client_common_set_hashes| contains the hashes of
   // the common sets known to the peer. |client_cached_cert_hashes| contains
   // 64-bit, FNV-1a hashes of certificates that the peer already possesses.
-  static QuicString CompressChain(const std::vector<QuicString>& certs,
-                                  QuicStringPiece client_common_set_hashes,
-                                  QuicStringPiece client_cached_cert_hashes,
-                                  const CommonCertSets* common_sets);
+  static std::string CompressChain(const std::vector<std::string>& certs,
+                                   QuicStringPiece client_common_set_hashes,
+                                   QuicStringPiece client_cached_cert_hashes,
+                                   const CommonCertSets* common_sets);
 
   // DecompressChain decompresses the result of |CompressChain|, given in |in|,
   // into a series of certificates that are written to |out_certs|.
   // |cached_certs| contains certificates that the peer may have omitted and
   // |common_sets| contains the common certificate sets known locally.
   static bool DecompressChain(QuicStringPiece in,
-                              const std::vector<QuicString>& cached_certs,
+                              const std::vector<std::string>& cached_certs,
                               const CommonCertSets* common_sets,
-                              std::vector<QuicString>* out_certs);
+                              std::vector<std::string>* out_certs);
 };
 
 }  // namespace quic