Add HpackDecoder3, an adapter using HpackDecoder (in net/http2/hpack/decoder).

net/spdy/spdy_framer.cc

 // 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.
 
 #include "net/spdy/spdy_framer.h"
 
 #include <string.h>
 
 #include <algorithm>
 #include <cctype>
 #include <ios>
 #include <iterator>
 #include <list>
 #include <memory>
 #include <new>
 #include <string>
 #include <vector>
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_util.h"
 #include "net/quic/core/quic_flags.h"
 #include "net/spdy/hpack/hpack_constants.h"
 #include "net/spdy/hpack/hpack_decoder.h"
 #include "net/spdy/hpack/hpack_decoder2.h"
+#include "net/spdy/hpack/hpack_decoder3.h"
 #include "net/spdy/http2_frame_decoder_adapter.h"
 #include "net/spdy/spdy_bitmasks.h"
 #include "net/spdy/spdy_bug_tracker.h"
 #include "net/spdy/spdy_flags.h"
 #include "net/spdy/spdy_frame_builder.h"
 #include "net/spdy/spdy_frame_reader.h"
 #include "net/spdy/spdy_framer_decoder_adapter.h"
 #include "net/spdy/spdy_headers_block_parser.h"
 
 using base::StringPiece;
@@ skipping 2426 matching lines @@
     hpack_encoder_.reset(new HpackEncoder(ObtainHpackHuffmanTable()));
     if (!compression_enabled()) {
       hpack_encoder_->DisableCompression();
     }
   }
   return hpack_encoder_.get();
 }
 
 HpackDecoderInterface* SpdyFramer::GetHpackDecoder() {
   if (hpack_decoder_.get() == nullptr) {
-    if (FLAGS_chromium_http2_flag_spdy_use_hpack_decoder2) {
+    if (FLAGS_chromium_http2_flag_spdy_use_hpack_decoder3) {
+      SPDY_BUG_IF(FLAGS_chromium_http2_flag_spdy_use_hpack_decoder2)
+          << "Both alternate decoders are enabled.";
+      hpack_decoder_.reset(new HpackDecoder3());
+    } else if (FLAGS_chromium_http2_flag_spdy_use_hpack_decoder2) {
       hpack_decoder_.reset(new HpackDecoder2());
     } else {
       hpack_decoder_.reset(new HpackDecoder());
     }
   }
   return hpack_decoder_.get();
 }
 
 bool SpdyFramer::IncrementallyDeliverControlFrameHeaderData(
     SpdyStreamId stream_id, const char* data, size_t len) {
@@ skipping 53 matching lines @@
   builder->WriteUInt32(header_block.size());
 
   // Serialize each header.
   for (const auto& header : header_block) {
     builder->WriteStringPiece32(base::ToLowerASCII(header.first));
     builder->WriteStringPiece32(header.second);
   }
 }
 
 }  // namespace net