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/quic_server_id.h b/quic/core/quic_server_id.h
index 62c0fda..33a0f0a 100644
--- a/quic/core/quic_server_id.h
+++ b/quic/core/quic_server_id.h
@@ -17,8 +17,8 @@
 class QUIC_EXPORT_PRIVATE QuicServerId {
  public:
   QuicServerId();
-  QuicServerId(const QuicString& host, uint16_t port);
-  QuicServerId(const QuicString& host,
+  QuicServerId(const std::string& host, uint16_t port);
+  QuicServerId(const std::string& host,
                uint16_t port,
                bool privacy_mode_enabled);
   ~QuicServerId();
@@ -27,7 +27,7 @@
   bool operator<(const QuicServerId& other) const;
   bool operator==(const QuicServerId& other) const;
 
-  const QuicString& host() const { return host_; }
+  const std::string& host() const { return host_; }
 
   uint16_t port() const { return port_; }
 
@@ -36,7 +36,7 @@
   size_t EstimateMemoryUsage() const;
 
  private:
-  QuicString host_;
+  std::string host_;
   uint16_t port_;
   bool privacy_mode_enabled_;
 };