Do not use SpdyFrameBuilder::OverwriteLength().

net/spdy/spdy_framer.h

 // 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.
 
 #ifndef NET_SPDY_SPDY_FRAMER_H_
 #define NET_SPDY_SPDY_FRAMER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 747 matching lines @@
 
   // If a HEADERS frame is followed by a CONTINUATION frame, the FIN/END_STREAM
   // flag is still carried in the HEADERS frame. If it's set, flip this so that
   // we know to terminate the stream when the entire header block has been
   // processed.
   bool end_stream_when_done_;
 
   // If true, then ProcessInput returns after processing a full frame,
   // rather than reading all available input.
   bool process_single_input_frame_ = false;
+
+  // Latched value of FLAGS_chromium_http2_flag_remove_rewritelength.
+  bool skip_rewritelength_ = false;
 };
 
 }  // namespace net
 
 #endif  // NET_SPDY_SPDY_FRAMER_H_