Remove NetPrefObserver class and two prefs that do not do anything.

chrome/chrome_browser.gypi

 # Copyright 2012 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': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 2177 matching lines @@
       'browser/net/dns_probe_service.h',
       'browser/net/file_downloader.cc',
       'browser/net/file_downloader.h',
       'browser/net/http_server_properties_manager_factory.cc',
       'browser/net/http_server_properties_manager_factory.h',
       'browser/net/net_error_diagnostics_dialog.h',
       'browser/net/net_error_diagnostics_dialog_mac.cc',
       'browser/net/net_error_diagnostics_dialog_win.cc',
       'browser/net/net_error_tab_helper.cc',
       'browser/net/net_error_tab_helper.h',
-      'browser/net/net_pref_observer.cc',
-      'browser/net/net_pref_observer.h',
       'browser/net/nqe/ui_network_quality_estimator_service.cc',
       'browser/net/nqe/ui_network_quality_estimator_service.h',
       'browser/net/nqe/ui_network_quality_estimator_service_factory.cc',
       'browser/net/nqe/ui_network_quality_estimator_service_factory.h',
       'browser/net/prediction_options.cc',
       'browser/net/prediction_options.h',
       'browser/net/predictor.cc',
       'browser/net/predictor.h',
       'browser/net/probe_message.cc',
       'browser/net/probe_message.h',
@@ skipping 2133 matching lines @@
             '../components/components.gyp:rlz',
             '../components/components.gyp:search_engines',
             '../rlz/rlz.gyp:rlz_lib',
             'common',
           ],
         },
       ],
     }],
   ],
 }