Optimize chained string concatenation in SPDY code.

net/spdy/spdy_http_utils.cc

Index: net/spdy/spdy_http_utils.cc
diff --git a/net/spdy/spdy_http_utils.cc b/net/spdy/spdy_http_utils.cc
index c604880473c7c41666bf79e5b8a87e52033ceaf1..cfb24371d3850d0248100df4fb75af579fd102ea 100644
--- a/net/spdy/spdy_http_utils.cc
+++ b/net/spdy/spdy_http_utils.cc
@@ -202,9 +202,12 @@ GURL GetUrlFromHeaderBlock(const SpdyHeaderBlock& headers,
   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);
 }