Introduce a new framework for back-and-forth tracked/protected preferences migration.

base/base.gypi

 # Copyright (c) 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.
 
 {
   'target_defaults': {
     'variables': {
       'base_target': 0,
       'base_i18n_target': 0,
     },
@@ skipping 107 matching lines @@
           'compiler_specific.h',
           'containers/hash_tables.h',
           'containers/linked_list.h',
           'containers/mru_cache.h',
           'containers/scoped_ptr_hash_map.h',
           'containers/small_map.h',
           'containers/stack_container.h',
           'cpu.cc',
           'cpu.h',
           'critical_closure.h',
-          'critical_closure_ios.mm',
           'debug/alias.cc',
           'debug/alias.h',
           'debug/crash_logging.cc',
           'debug/crash_logging.h',
           'debug/debugger.cc',
           'debug/debugger.h',
           'debug/debugger_posix.cc',
           'debug/debugger_win.cc',
           'debug/dump_without_crashing.cc',
           'debug/dump_without_crashing.h',
           'debug/gdi_debug_util_win.cc',
-          'debug/gdi_debug_util_win.h',        
+          'debug/gdi_debug_util_win.h',
           # This file depends on files from the 'allocator' target,
           # but this target does not depend on 'allocator' (see
           # allocator.gyp for details).
           'debug/leak_annotations.h',
           'debug/leak_tracker.h',
           'debug/proc_maps_linux.cc',
           'debug/proc_maps_linux.h',
           'debug/profiler.cc',
           'debug/profiler.h',
           'debug/stack_trace.cc',
@@ skipping 803 matching lines @@
           'i18n/time_formatting.h',
           'i18n/timezone.cc',
           'i18n/timezone.h',
           'i18n/utf8_validator_tables.cc',
           'i18n/utf8_validator_tables.h',
         ],
       }]
     ],
   },
 }