Remove unused HostResolver::Observer.

net/net.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
 
     'linux_link_kerberos%': 0,
     'conditions': [
@@ skipping 1312 matching lines @@
         'base/cookie_store_test_helpers.cc',
         'base/cookie_store_test_helpers.h',
         'base/mock_file_stream.cc',
         'base/mock_file_stream.h',
         'base/mock_host_resolver.cc',
         'base/mock_host_resolver.h',
         'base/net_test_suite.cc',
         'base/net_test_suite.h',
         'base/test_completion_callback.cc',
         'base/test_completion_callback.h',
-        'base/test_host_resolver_observer.cc',
-        'base/test_host_resolver_observer.h',
         'disk_cache/disk_cache_test_util.cc',
         'disk_cache/disk_cache_test_util.h',
         'dns/dns_test_util.cc',
         'dns/dns_test_util.h',
         'proxy/mock_proxy_resolver.cc',
         'proxy/mock_proxy_resolver.h',
         'proxy/mock_proxy_script_fetcher.cc',
         'proxy/mock_proxy_script_fetcher.h',
         'proxy/proxy_config_service_common_unittest.cc',
         'proxy/proxy_config_service_common_unittest.h',
@@ skipping 289 matching lines @@
             'tools/dump_cache/url_to_filename_encoder.cc',
             'tools/dump_cache/url_to_filename_encoder.h',
             'tools/dump_cache/url_utilities.h',
             'tools/dump_cache/url_utilities.cc',
           ],
         },
       ],
     }],
   ],
 }