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_control_frame_manager.cc b/quic/core/quic_control_frame_manager.cc
index 8d4ba53..5fd756f 100644
--- a/quic/core/quic_control_frame_manager.cc
+++ b/quic/core/quic_control_frame_manager.cc
@@ -47,7 +47,7 @@
 void QuicControlFrameManager::WriteOrBufferGoAway(
     QuicErrorCode error,
     QuicStreamId last_good_stream_id,
-    const QuicString& reason) {
+    const std::string& reason) {
   QUIC_DVLOG(1) << "Writing GOAWAY_FRAME";
   WriteOrBufferQuicFrame(QuicFrame(new QuicGoAwayFrame(
       ++last_control_frame_id_, error, last_good_stream_id, reason)));