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/frames/quic_new_token_frame.h b/quic/core/frames/quic_new_token_frame.h
index 6fb0ea4..5a063a3 100644
--- a/quic/core/frames/quic_new_token_frame.h
+++ b/quic/core/frames/quic_new_token_frame.h
@@ -17,7 +17,7 @@
 
 struct QUIC_EXPORT_PRIVATE QuicNewTokenFrame {
   QuicNewTokenFrame();
-  QuicNewTokenFrame(QuicControlFrameId control_frame_id, QuicString token);
+  QuicNewTokenFrame(QuicControlFrameId control_frame_id, std::string token);
 
   friend QUIC_EXPORT_PRIVATE std::ostream& operator<<(
       std::ostream& os,
@@ -27,7 +27,7 @@
   // and non-zero when sent.
   QuicControlFrameId control_frame_id;
 
-  QuicString token;
+  std::string token;
 };
 static_assert(sizeof(QuicNewTokenFrame) <= 64,
               "Keep the QuicNewTokenFrame size to a cacheline.");