Fix a QuicStreamSequencerBuffer logging issue caused by inapproriate itoa function.

net/quic/quic_stream_sequencer_buffer.cc

Index: net/quic/quic_stream_sequencer_buffer.cc
diff --git a/net/quic/quic_stream_sequencer_buffer.cc b/net/quic/quic_stream_sequencer_buffer.cc
index dabb2ce37090eeac8c1005dc59595ae35be3af44..0f56bf96db4908edd20755cc36fcb4f5fef476f7 100644
--- a/net/quic/quic_stream_sequencer_buffer.cc
+++ b/net/quic/quic_stream_sequencer_buffer.cc
@@ -16,8 +16,8 @@ namespace net {
 namespace {
 
 string RangeDebugString(QuicStreamOffset start, QuicStreamOffset end) {
-  return string("[") + base::IntToString(start) + ", " +
-         base::IntToString(end) + ") ";
+  return string("[") + base::Uint64ToString(start) + ", " +
+         base::Uint64ToString(end) + ") ";
 }
 
 }  // namespace