Preparation for only writing a fraction of the iov due to flow control

net/quic/reliable_quic_stream.cc

Index: net/quic/reliable_quic_stream.cc
diff --git a/net/quic/reliable_quic_stream.cc b/net/quic/reliable_quic_stream.cc
index 946865db0607f36202cfc3381123b57693f8d29f..a37affe8184ed935c44e863b3f697b6d49342eb4 100644
--- a/net/quic/reliable_quic_stream.cc
+++ b/net/quic/reliable_quic_stream.cc
@@ -182,8 +182,13 @@ QuicConsumedData ReliableQuicStream::WritevData(
     write_length += iov[i].iov_len;
     // TODO(rjshade): Maybe block write based on available flow control window.
   }
+
+  // Fill an IOVector with bytes from the iovec.
+  IOVector data;
+  data.AppendIovecAtMostBytes(iov, iov_count, write_length);
+
   QuicConsumedData consumed_data = session()->WritevData(
-      id(), iov, iov_count, stream_bytes_written_, fin, ack_notifier_delegate);
+      id(), data, stream_bytes_written_, fin, ack_notifier_delegate);
   stream_bytes_written_ += consumed_data.bytes_consumed;
   if (consumed_data.bytes_consumed == write_length) {
     if (fin && consumed_data.fin_consumed) {