Revert of Avoids the "re-encode HPACK as SPDY3" step.

net/spdy/header_coalescer.cc

-// Copyright (c) 2016 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/header_coalescer.h"
-
-#include "base/strings/string_util.h"
-
-namespace net {
-
-void HeaderCoalescer::OnHeader(base::StringPiece key, base::StringPiece value) {
-  if (key.empty()) {
-    DVLOG(1) << "Header name must not be empty.";
-    error_seen_ = true;
-    return;
-  }
-
-  auto iter = headers_.find(key);
-  if (iter == headers_.end()) {
-    headers_[key] = value;
-  } else {
-    // This header had multiple values, so it must be reconstructed.
-    base::StringPiece v = iter->second;
-    std::string s(v.data(), v.length());
-    if (key == "cookie") {
-      // Obeys section 8.1.2.5 in RFC 7540 for cookie reconstruction.
-      s.append("; ");
-    } else {
-      base::StringPiece("\0", 1).AppendToString(&s);
-    }
-    value.AppendToString(&s);
-    headers_.ReplaceOrAppendHeader(key, s);
-  }
-}
-
-}  // namespace net