Reduce SpdyHeaderBlock copies with move semantics in shared code.

net/quic/quic_spdy_stream.cc

Index: net/quic/quic_spdy_stream.cc
diff --git a/net/quic/quic_spdy_stream.cc b/net/quic/quic_spdy_stream.cc
index f1a21d4e8dc568c295117ecb3c7bbceecab0e2f3..d0af94d2bbca2aa8f25722b8a5e1438919ae86c7 100644
--- a/net/quic/quic_spdy_stream.cc
+++ b/net/quic/quic_spdy_stream.cc
@@ -4,6 +4,8 @@
 
 #include "net/quic/quic_spdy_stream.h"
 
+#include <utility>
+
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "net/quic/quic_bug_tracker.h"
@@ -68,11 +70,11 @@ void QuicSpdyStream::StopReading() {
 }
 
 size_t QuicSpdyStream::WriteHeaders(
-    const SpdyHeaderBlock& header_block,
+    SpdyHeaderBlock header_block,
     bool fin,
     QuicAckListenerInterface* ack_notifier_delegate) {
   size_t bytes_written = spdy_session_->WriteHeaders(
-      id(), header_block, fin, priority_, ack_notifier_delegate);
+      id(), std::move(header_block), fin, priority_, ack_notifier_delegate);
   if (fin) {
     // TODO(rch): Add test to ensure fin_sent_ is set whenever a fin is sent.
     set_fin_sent(true);
@@ -89,7 +91,7 @@ void QuicSpdyStream::WriteOrBufferBody(
 }
 
 size_t QuicSpdyStream::WriteTrailers(
-    const SpdyHeaderBlock& trailer_block,
+    SpdyHeaderBlock trailer_block,
     QuicAckListenerInterface* ack_notifier_delegate) {
   if (fin_sent()) {
     QUIC_BUG << "Trailers cannot be sent after a FIN.";
@@ -100,8 +102,7 @@ size_t QuicSpdyStream::WriteTrailers(
   // trailers may be processed out of order at the peer.
   DVLOG(1) << "Inserting trailer: (" << kFinalOffsetHeaderKey << ", "
            << stream_bytes_written() + queued_data_bytes() << ")";
-  SpdyHeaderBlock trailer_block_with_offset(trailer_block);
-  trailer_block_with_offset.insert(std::make_pair(
+  trailer_block.insert(std::make_pair(
       kFinalOffsetHeaderKey,
       base::IntToString(stream_bytes_written() + queued_data_bytes())));
 
@@ -109,7 +110,7 @@ size_t QuicSpdyStream::WriteTrailers(
   // trailers are the last thing to be sent on a stream.
   const bool kFin = true;
   size_t bytes_written = spdy_session_->WriteHeaders(
-      id(), trailer_block_with_offset, kFin, priority_, ack_notifier_delegate);
+      id(), std::move(trailer_block), kFin, priority_, ack_notifier_delegate);
   set_fin_sent(kFin);
 
   // Trailers are the last thing to be sent on a stream, but if there is still
@@ -279,7 +280,6 @@ void QuicSpdyStream::OnTrailingHeadersComplete(bool fin, size_t /*frame_len*/) {
   }
 
   size_t final_byte_offset = 0;
-  SpdyHeaderBlock trailers;
   if (!SpdyUtils::ParseTrailers(decompressed_trailers().data(),
                                 decompressed_trailers().length(),
                                 &final_byte_offset, &received_trailers_)) {