Remove SingleHostResolver completely.

net/dns/single_request_host_resolver.cc

-// 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.
-
-#include "net/dns/single_request_host_resolver.h"
-
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/compiler_specific.h"
-#include "base/logging.h"
-#include "net/base/net_errors.h"
-
-namespace net {
-
-SingleRequestHostResolver::SingleRequestHostResolver(HostResolver* resolver)
-    : resolver_(resolver),
-      callback_(
-          base::Bind(&SingleRequestHostResolver::OnResolveCompletion,
-                     base::Unretained(this))) {
-  DCHECK(resolver_ != nullptr);
-}
-
-SingleRequestHostResolver::~SingleRequestHostResolver() {
-  Cancel();
-}
-
-int SingleRequestHostResolver::Resolve(const HostResolver::RequestInfo& info,
-                                       RequestPriority priority,
-                                       AddressList* addresses,
-                                       const CompletionCallback& callback,
-                                       const BoundNetLog& net_log) {
-  DCHECK(addresses);
-  DCHECK_EQ(false, callback.is_null());
-  DCHECK(cur_request_callback_.is_null()) << "resolver already in use";
-
-  std::unique_ptr<HostResolver::Request> request;
-
-  // We need to be notified of completion before |callback| is called, so that
-  // we can clear out |cur_request_*|.
-  CompletionCallback transient_callback =
-      callback.is_null() ? CompletionCallback() : callback_;
-
-  int rv = resolver_->Resolve(
-      info, priority, addresses, transient_callback, &request, net_log);
-
-  if (rv == ERR_IO_PENDING) {
-    DCHECK_EQ(false, callback.is_null());
-    // Cleared in OnResolveCompletion().
-    cur_request_ = std::move(request);
-    cur_request_callback_ = callback;
-  }
-
-  return rv;
-}
-
-void SingleRequestHostResolver::Cancel() {
-  cur_request_.reset();
-  cur_request_callback_.Reset();
-}
-
-void SingleRequestHostResolver::OnResolveCompletion(int result) {
-  DCHECK(cur_request_);
-  DCHECK_EQ(false, cur_request_callback_.is_null());
-
-  CompletionCallback callback = cur_request_callback_;
-
-  // Clear the outstanding request information.
-  cur_request_.reset();
-  cur_request_callback_.Reset();
-
-  // Call the user's original callback.
-  callback.Run(result);
-}
-
-}  // namespace net