Optimize chained string concatenation in SPDY code.

net/spdy/spdy_stream.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_stream.h"
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 331 matching lines @@
 
 void SpdyStream::DecreaseRecvWindowSize(int32 delta_window_size) {
   DCHECK(session_->IsStreamActive(stream_id_));
   DCHECK_GE(session_->flow_control_state(), SpdySession::FLOW_CONTROL_STREAM);
   DCHECK_GE(delta_window_size, 1);
 
   // Since we never decrease the initial receive 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;
   }
 
   recv_window_size_ -= delta_window_size;
   net_log_.AddEvent(
       NetLog::TYPE_SPDY_STREAM_UPDATE_RECV_WINDOW,
       base::Bind(&NetLogSpdyStreamWindowUpdateCallback,
                  stream_id_, -delta_window_size, recv_window_size_));
 }
 
@@ skipping 546 matching lines @@
       description = base::StringPrintf("Unknown state 0x%08X (%u)", state,
                                        state);
       break;
   }
   return description;
 }
 
 #undef STATE_CASE
 
 }  // namespace net