Brushed up listen socket:

net/tools/fetch/http_listen_socket.cc

Index: net/tools/fetch/http_listen_socket.cc
diff --git a/net/tools/fetch/http_listen_socket.cc b/net/tools/fetch/http_listen_socket.cc
index 033afc40010003e644def7dc1e9035a21401c36b..e135322574c5e83d2a1e57e47bc562bff61b23d7 100644
--- a/net/tools/fetch/http_listen_socket.cc
+++ b/net/tools/fetch/http_listen_socket.cc
@@ -182,8 +182,9 @@ void HttpListenSocket::DidAccept(ListenSocket* server,
 }
 
 void HttpListenSocket::DidRead(ListenSocket* connection,
-                               const std::string& data) {
-  recv_data_ += data;
+                               const char* data,
+                               int len) {
+  recv_data_.append(data, len);
   while (recv_data_.length()) {
     HttpServerRequestInfo* request = ParseHeaders();
     if (!request)