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/tools/quic_simple_server_stream.cc b/quic/tools/quic_simple_server_stream.cc
index 541ff32..4e25552 100644
--- a/quic/tools/quic_simple_server_stream.cc
+++ b/quic/tools/quic_simple_server_stream.cc
@@ -155,7 +155,7 @@
   return id();
 }
 
-QuicString QuicSimpleServerStream::peer_host() const {
+std::string QuicSimpleServerStream::peer_host() const {
   return spdy_session()->peer_address().host().ToString();
 }
 
@@ -192,8 +192,8 @@
   // response status, send error response. Notice that
   // QuicHttpResponseCache push urls are strictly authority + path only,
   // scheme is not included (see |QuicHttpResponseCache::GetKey()|).
-  QuicString request_url = request_headers_[":authority"].as_string() +
-                           request_headers_[":path"].as_string();
+  std::string request_url = request_headers_[":authority"].as_string() +
+                            request_headers_[":path"].as_string();
   int response_code;
   const SpdyHeaderBlock& response_headers = response->headers();
   if (!ParseHeaderStatusCode(response_headers, &response_code)) {