sync: Introduce ModelTypeRegistry and helpers

sync/sync_tests.gypi

 # Copyright 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': [
     # Test support files for the 'sync_core' target.
     {
       'target_name': 'test_support_sync_core',
       'type': 'static_library',
@@ skipping 227 matching lines @@
           'internal_api/public/base/enum_set_unittest.cc',
           'internal_api/public/base/node_ordinal_unittest.cc',
           'internal_api/public/base/ordinal_unittest.cc',
           'internal_api/public/base/unique_position_unittest.cc',
           'internal_api/public/engine/model_safe_worker_unittest.cc',
           'internal_api/public/util/immutable_unittest.cc',
           'internal_api/public/util/weak_handle_unittest.cc',
           'engine/apply_control_data_updates_unittest.cc',
           'engine/backoff_delay_provider_unittest.cc',
           'engine/download_unittest.cc',
+          'engine/sync_directory_commit_contribution_unittest.cc',
+          'engine/sync_directory_update_handler_unittest.cc',
           'engine/sync_scheduler_unittest.cc',
           'engine/syncer_proto_util_unittest.cc',
           'engine/syncer_unittest.cc',
-          'engine/sync_directory_commit_contribution_unittest.cc',
-          'engine/sync_directory_update_handler_unittest.cc',
           'engine/traffic_recorder_unittest.cc',
           'js/js_arg_list_unittest.cc',
           'js/js_event_details_unittest.cc',
           'js/sync_js_controller_unittest.cc',
           'protocol/proto_enum_conversions_unittest.cc',
           'protocol/proto_value_conversions_unittest.cc',
+          'sessions/model_type_registry_unittest.cc',
           'sessions/nudge_tracker_unittest.cc',
           'sessions/status_controller_unittest.cc',
-          'sessions/sync_session_unittest.cc',
           'syncable/directory_backing_store_unittest.cc',
           'syncable/model_type_unittest.cc',
           'syncable/nigori_util_unittest.cc',
           'syncable/parent_child_index_unittest.cc',
           'syncable/syncable_enum_conversions_unittest.cc',
           'syncable/syncable_id_unittest.cc',
           'syncable/syncable_unittest.cc',
           'syncable/syncable_util_unittest.cc',
           'util/cryptographer_unittest.cc',
           'util/data_type_histogram_unittest.cc',
@@ skipping 351 matching lines @@
           'variables': {
             'test_suite_name': 'sync_unit_tests',
             'input_shlib_path': '<(SHARED_LIB_DIR)/<(SHARED_LIB_PREFIX)sync_unit_tests<(SHARED_LIB_SUFFIX)',
           },
           'includes': [ '../build/apk_test.gypi' ],
         },
       ],
     }],
   ],
 }