Optimize chained string concatenation in SPDY code.

net/spdy/spdy_stream.cc

Index: net/spdy/spdy_stream.cc
diff --git a/net/spdy/spdy_stream.cc b/net/spdy/spdy_stream.cc
index e7dcd5b95d5e2aa82c5e47a0cb50058e98ec514a..9e39000f5be41346323560fedccb63c5c9aff79f 100644
--- a/net/spdy/spdy_stream.cc
+++ b/net/spdy/spdy_stream.cc
@@ -349,11 +349,13 @@ void SpdyStream::DecreaseRecvWindowSize(int32 delta_window_size) {
   // |delta_window_size| should never cause |recv_window_size_| to go
   // negative. If we do, the receive window isn't being respected.
   if (delta_window_size > recv_window_size_) {
-    session_->ResetStream(
-        stream_id_, RST_STREAM_PROTOCOL_ERROR,
-        "delta_window_size is " + base::IntToString(delta_window_size) +
-            " in DecreaseRecvWindowSize, which is larger than the receive " +
-            "window size of " + base::IntToString(recv_window_size_));
+    session_->ResetStream(stream_id_, RST_STREAM_PROTOCOL_ERROR,
+                          std::string("delta_window_size is ")
+                              .append(base::IntToString(delta_window_size))
+                              .append(
+                                   " in DecreaseRecvWindowSize, which is "
+                                   "larger than the receive window size of ")
+                              .append(base::IntToString(recv_window_size_)));

[mmenke, 2015/03/09 20:21:58]

Worth considering std::StringPrintf here, too?

     return;
   }