Remove HTTP pipelining support.

net/http/http_pipelined_host_capability.h

-// Copyright (c) 2011 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_HTTP_HTTP_PIPELINED_HOST_CAPABILITY_H_
-#define NET_HTTP_HTTP_PIPELINED_HOST_CAPABILITY_H_
-
-namespace net {
-
-// These values are serialized in Preferences. Do not change these values and
-// only add new ones at the end.
-enum HttpPipelinedHostCapability {
-  PIPELINE_UNKNOWN = 0,
-  PIPELINE_INCAPABLE = 1,
-  PIPELINE_CAPABLE = 2,
-  PIPELINE_PROBABLY_CAPABLE = 3,  // We are using pipelining, but haven't
-                                  // processed enough requests to record this
-                                  // host as known to be capable.
-};
-
-}  // namespace net
-
-#endif  // NET_HTTP_HTTP_PIPELINED_HOST_CAPABILITY_H_