Reduce SpdyHeaderBlock copies with move semantics.

net/spdy/spdy_session.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_SESSION_H_
 #define NET_SPDY_SPDY_SESSION_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 354 matching lines @@
   bool VerifyDomainAuthentication(const std::string& domain);
 
   // Pushes the given producer into the write queue for
   // |stream|. |stream| is guaranteed to be activated before the
   // producer is used to produce its frame.
   void EnqueueStreamWrite(const base::WeakPtr<SpdyStream>& stream,
                           SpdyFrameType frame_type,
                           std::unique_ptr<SpdyBufferProducer> producer);
 
   // Creates and returns a SYN frame for |stream_id|.
-  std::unique_ptr<SpdySerializedFrame> CreateSynStream(
-      SpdyStreamId stream_id,
-      RequestPriority priority,
-      SpdyControlFlags flags,
-      const SpdyHeaderBlock& headers);
+  std::unique_ptr<SpdySerializedFrame> CreateSynStream(SpdyStreamId stream_id,
+                                                       RequestPriority priority,
+                                                       SpdyControlFlags flags,
+                                                       SpdyHeaderBlock headers);
 
   // Creates and returns a SpdyBuffer holding a data frame with the
   // given data. May return NULL if stalled by flow control.
   std::unique_ptr<SpdyBuffer> CreateDataBuffer(SpdyStreamId stream_id,
                                                IOBuffer* data,
                                                int len,
                                                SpdyDataFlags flags);
 
   // Close the stream with the given ID, which must exist and be
   // active. Note that that stream may hold the last reference to the
@@ skipping 846 matching lines @@
   // Used for posting asynchronous IO tasks.  We use this even though
   // SpdySession is refcounted because we don't need to keep the SpdySession
   // alive if the last reference is within a RunnableMethod.  Just revoke the
   // method.
   base::WeakPtrFactory<SpdySession> weak_factory_;
 };
 
 }  // namespace net
 
 #endif  // NET_SPDY_SPDY_SESSION_H_