Clean up old legacy preference migration logic.

components/user_prefs.gypi

 # Copyright (c) 2013 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.
 
 {
   'targets': [
     {
       'target_name': 'user_prefs',
       'type': '<(component)',
       'dependencies': [
@@ skipping 33 matching lines @@
         'user_prefs/tracked/pref_hash_calculator.cc',
         'user_prefs/tracked/pref_hash_calculator.h',
         'user_prefs/tracked/pref_hash_filter.cc',
         'user_prefs/tracked/pref_hash_filter.h',
         'user_prefs/tracked/pref_hash_store.h',
         'user_prefs/tracked/pref_hash_store_impl.cc',
         'user_prefs/tracked/pref_hash_store_impl.h',
         'user_prefs/tracked/pref_hash_store_transaction.h',
         'user_prefs/tracked/pref_names.cc',
         'user_prefs/tracked/pref_names.h',
-        'user_prefs/tracked/pref_service_hash_store_contents.cc',
-        'user_prefs/tracked/pref_service_hash_store_contents.h',
         'user_prefs/tracked/segregated_pref_store.cc',
         'user_prefs/tracked/segregated_pref_store.h',
         'user_prefs/tracked/tracked_atomic_preference.cc',
         'user_prefs/tracked/tracked_atomic_preference.h',
         'user_prefs/tracked/tracked_preference.h',
         'user_prefs/tracked/tracked_preference_helper.cc',
         'user_prefs/tracked/tracked_preference_helper.h',
         'user_prefs/tracked/tracked_preference_histogram_names.cc',
         'user_prefs/tracked/tracked_preference_histogram_names.h',
         'user_prefs/tracked/tracked_preference_validation_delegate.h',
@@ skipping 26 matching lines @@
       ],
       'dependencies': [
       ],
       'sources': [
         'user_prefs/tracked/mock_validation_delegate.cc',
         'user_prefs/tracked/mock_validation_delegate.h',
       ],
     },
   ],
 }