Add QuicStrCat.

net/quic/core/quic_stream_sequencer.cc

Index: net/quic/core/quic_stream_sequencer.cc
diff --git a/net/quic/core/quic_stream_sequencer.cc b/net/quic/core/quic_stream_sequencer.cc
index 64c6b4c1a6981f150de6b076cf2e5187b9b57e51..a67176717ad2e2b108fa88a6086e7f8493b14f29 100644
--- a/net/quic/core/quic_stream_sequencer.cc
+++ b/net/quic/core/quic_stream_sequencer.cc
@@ -20,6 +20,7 @@
 #include "net/quic/core/quic_stream_sequencer_buffer.h"
 #include "net/quic/core/quic_utils.h"
 #include "net/quic/platform/api/quic_clock.h"
+#include "net/quic/platform/api/quic_str_cat.h"
 
 using base::IntToString;
 using base::StringPiece;
@@ -58,10 +59,10 @@ void QuicStreamSequencer::OnStreamFrame(const QuicStreamFrame& frame) {
       byte_offset, StringPiece(frame.data_buffer, frame.data_length),
       clock_->ApproximateNow(), &bytes_written, &error_details);
   if (result != QUIC_NO_ERROR) {
-    string details = "Stream" + base::Uint64ToString(stream_->id()) + ": " +
-                     QuicErrorCodeToString(result) + ": " + error_details +
-                     "\nPeer Address: " +
-                     stream_->PeerAddressOfLatestPacket().ToString();
+    string details = QuicStrCat(
+        "Stream ", stream_->id(), ": ", QuicErrorCodeToString(result), ": ",
+        error_details, "\nPeer Address: ",
+        stream_->PeerAddressOfLatestPacket().ToString());
     DLOG(WARNING) << QuicErrorCodeToString(result);
     DLOG(WARNING) << details;
     stream_->CloseConnectionWithDetails(result, details);
@@ -142,8 +143,7 @@ int QuicStreamSequencer::Readv(const struct iovec* iov, size_t iov_len) {
   QuicErrorCode read_error =
       buffered_frames_.Readv(iov, iov_len, &bytes_read, &error_details);
   if (read_error != QUIC_NO_ERROR) {
-    string details = StringPrintf("Stream %" PRIu32 ": %s", stream_->id(),
-                                  error_details.c_str());
+    string details = QuicStrCat("Stream ", stream_->id(), ": ", error_details);
     stream_->CloseConnectionWithDetails(read_error, details);
     return static_cast<int>(bytes_read);
   }
@@ -222,13 +222,13 @@ QuicStreamOffset QuicStreamSequencer::NumBytesConsumed() const {
 
 const string QuicStreamSequencer::DebugString() const {
   // clang-format off
-  return "QuicStreamSequencer:"
-         "\n  bytes buffered: " + IntToString(NumBytesBuffered()) +
-         "\n  bytes consumed: " + IntToString( NumBytesConsumed()) +
-         "\n  has bytes to read: " +  (HasBytesToRead() ? "true" : "false") +
-         "\n  frames received: " + IntToString(num_frames_received()) +
-         "\n  close offset bytes: " + IntToString( close_offset_) +
-         "\n  is closed: " + (IsClosed() ? "true" : "false");
+  return QuicStrCat("QuicStreamSequencer:",
+                "\n  bytes buffered: ", NumBytesBuffered(),
+                "\n  bytes consumed: ", NumBytesConsumed(),
+                "\n  has bytes to read: ", HasBytesToRead() ? "true" : "false",
+                "\n  frames received: ", num_frames_received(),
+                "\n  close offset bytes: ", close_offset_,
+                "\n  is closed: ", IsClosed() ? "true" : "false");
   // clang-format on
 }