Reduce SpdyHeaderBlock copies with move semantics in shared code.

net/quic/quic_spdy_stream.h

 // Copyright 2013 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.
 //
 // The base class for streams which deliver data to/from an application.
 // In each direction, the data on such a stream first contains compressed
 // headers then body data.
 
 #ifndef NET_QUIC_QUIC_SPDY_STREAM_H_
 #define NET_QUIC_QUIC_SPDY_STREAM_H_
@@ skipping 102 matching lines @@
   virtual void OnPromiseHeaderList(QuicStreamId promised_id,
                                    size_t frame_len,
                                    const QuicHeaderList& header_list);
 
   // Override the base class to not discard response when receiving
   // QUIC_STREAM_NO_ERROR on QUIC_VERSION_29 and later versions.
   void OnStreamReset(const QuicRstStreamFrame& frame) override;
 
   // Writes the headers contained in |header_block| to the dedicated
   // headers stream.
-  virtual size_t WriteHeaders(const SpdyHeaderBlock& header_block,
+  virtual size_t WriteHeaders(SpdyHeaderBlock header_block,
                               bool fin,
                               QuicAckListenerInterface* ack_notifier_delegate);
 
   // Sends |data| to the peer, or buffers if it can't be sent immediately.
   void WriteOrBufferBody(const std::string& data,
                          bool fin,
                          QuicAckListenerInterface* ack_notifier_delegate);
 
   // Writes the trailers contained in |trailer_block| to the dedicated
   // headers stream. Trailers will always have the FIN set.
-  virtual size_t WriteTrailers(const SpdyHeaderBlock& trailer_block,
+  virtual size_t WriteTrailers(SpdyHeaderBlock trailer_block,
                                QuicAckListenerInterface* ack_notifier_delegate);
 
   // Marks |bytes_consumed| of the headers data as consumed.
   void MarkHeadersConsumed(size_t bytes_consumed);
 
   // Marks |bytes_consumed| of the trailers data as consumed.
   void MarkTrailersConsumed(size_t bytes_consumed);
 
   // Marks the trailers as consumed.
   void MarkTrailersDelivered();
@@ skipping 95 matching lines @@
   std::string decompressed_trailers_;
   // The parsed trailers received from the peer.
   SpdyHeaderBlock received_trailers_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicSpdyStream);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_SPDY_STREAM_H_