Make proxy settings one atomic dictionary in the PrefStores such that modifications are atomic.

chrome/chrome_tests.gypi

 # 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' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
@@ skipping 1330 matching lines @@
         'browser/preferences_mock_mac.h',
         'browser/prefs/command_line_pref_store_unittest.cc',
         'browser/prefs/overlay_persistent_pref_store_unittest.cc',
         'browser/prefs/pref_change_registrar_unittest.cc',
         'browser/prefs/pref_member_unittest.cc',
         'browser/prefs/pref_notifier_impl_unittest.cc',
         'browser/prefs/pref_service_unittest.cc',
         'browser/prefs/pref_set_observer_unittest.cc',
         'browser/prefs/pref_value_map_unittest.cc',
         'browser/prefs/pref_value_store_unittest.cc',
+        'browser/prefs/proxy_config_dictionary_unittest.cc',
         'browser/prefs/proxy_prefs_unittest.cc',
         'browser/prefs/session_startup_pref_unittest.cc',
         'browser/prerender/prerender_manager_unittest.cc',
         'browser/prerender/prerender_resource_handler_unittest.cc',
         'browser/printing/cloud_print/cloud_print_setup_source_unittest.cc',
         'browser/printing/print_dialog_cloud_unittest.cc',
         'browser/printing/print_job_unittest.cc',
         'browser/printing/print_preview_tab_controller_unittest.cc',
         'browser/process_info_snapshot_mac_unittest.cc',
         'browser/process_singleton_mac_unittest.cc',
@@ skipping 2336 matching lines @@
       ]
     }],  # 'coverage!=0'
   ],  # 'conditions'
 }
 
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