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/http/quic_spdy_session.h b/quic/core/http/quic_spdy_session.h
index 93067fa..c13daeb 100644
--- a/quic/core/http/quic_spdy_session.h
+++ b/quic/core/http/quic_spdy_session.h
@@ -153,7 +153,7 @@
   virtual bool ShouldReleaseHeadersStreamSequencerBuffer();
 
   void CloseConnectionWithDetails(QuicErrorCode error,
-                                  const QuicString& details);
+                                  const std::string& details);
 
   void set_max_inbound_header_list_size(size_t max_inbound_header_list_size) {
     max_inbound_header_list_size_ = max_inbound_header_list_size;