Optimize chained string concatenation in SPDY code.

net/spdy/spdy_http_utils.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/spdy/spdy_http_utils.h"
 
 #include <string>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ skipping 184 matching lines @@
   it = headers.find(scheme_header);
   if (it != headers.end())
     scheme = it->second;
   it = headers.find(host_header);
   if (it != headers.end())
     host_port = it->second;
   it = headers.find(path_header);
   if (it != headers.end())
     path = it->second;
 
-  std::string url = (scheme.empty() || host_port.empty() || path.empty())
-                        ? std::string()
-                        : scheme + "://" + host_port + path;
+  std::string url = scheme;

[Bence, 2015/03/09 19:53:46]

You don't seem to be conserving behavior here:  In the original code, |url| is
empty if any of scheme, host_port, and path is empty.

+  if (!scheme.empty() && !host_port.empty() && path.empty()) {
+    url += "://";
+    url += host_port;
+    url += path;
+  }
   return GURL(url);
 }
 
 }  // namespace net