[Sync] Add ModelTypeStore implementation.

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.
     # GN version: //sync:test_support_sync_core
     {
       'target_name': 'test_support_sync_core',
@@ skipping 281 matching lines @@
         'internal_api/attachments/fake_attachment_downloader_unittest.cc',
         'internal_api/attachments/fake_attachment_uploader_unittest.cc',
         'internal_api/attachments/in_memory_attachment_store_unittest.cc',
         'internal_api/attachments/on_disk_attachment_store_unittest.cc',
         'internal_api/attachments/task_queue_unittest.cc',
         'internal_api/debug_info_event_listener_unittest.cc',
         'internal_api/http_bridge_unittest.cc',
         'internal_api/js_mutation_event_observer_unittest.cc',
         'internal_api/js_sync_encryption_handler_observer_unittest.cc',
         'internal_api/js_sync_manager_observer_unittest.cc',
+        'internal_api/model_type_store_impl_unittest.cc',
         'internal_api/protocol_event_buffer_unittest.cc',
         'internal_api/public/base/attachment_id_proto_unittest.cc',
         'internal_api/public/base/cancelation_signal_unittest.cc',
         '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/change_record_unittest.cc',
         'internal_api/public/engine/model_safe_worker_unittest.cc',
         'internal_api/public/sessions/sync_session_snapshot_unittest.cc',
@@ skipping 224 matching lines @@
             '../build/isolate.gypi',
           ],
           'sources': [
             'sync_unit_tests.isolate',
           ],
         },
       ],
     }],
   ],
 }