Remove unused HostResolver::Observer.

net/base/mapped_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/base/mapped_host_resolver.h"
 
 #include "base/string_tokenizer.h"
 #include "base/string_util.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/net_errors.h"
@@ skipping 27 matching lines @@
                                          AddressList* addresses,
                                          const BoundNetLog& net_log) {
   NOTIMPLEMENTED();
   return ERR_UNEXPECTED;
 }
 
 void MappedHostResolver::CancelRequest(RequestHandle req) {
   impl_->CancelRequest(req);
 }
 
-void MappedHostResolver::AddObserver(Observer* observer) {
-  impl_->AddObserver(observer);
-}
-
-void MappedHostResolver::RemoveObserver(Observer* observer) {
-  impl_->RemoveObserver(observer);
-}
-
 void MappedHostResolver::ProbeIPv6Support() {
   impl_->ProbeIPv6Support();
 }
 
 HostCache* MappedHostResolver::GetHostCache() {
   return impl_->GetHostCache();
 }
 
 }  // namespace net