sync: Implement per-type commit interface

sync/sync_core.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.
 
 {
   'include_dirs': [
     '..',
   ],
   'defines': [
     'SYNC_IMPLEMENTATION',
@@ skipping 22 matching lines @@
     'engine/apply_control_data_updates.cc',
     'engine/apply_control_data_updates.h',
     'engine/apply_updates_and_resolve_conflicts_command.cc',
     'engine/apply_updates_and_resolve_conflicts_command.h',
     'engine/backoff_delay_provider.cc',
     'engine/backoff_delay_provider.h',
     'engine/build_commit_command.cc',
     'engine/build_commit_command.h',
     'engine/commit.cc',
     'engine/commit.h',
+    'engine/sync_directory_commit_contribution.cc',
+    'engine/sync_directory_commit_contribution.h',
+    'engine/sync_directory_commit_contributor.cc',
+    'engine/sync_directory_commit_contributor.h',
     'engine/conflict_resolver.cc',
     'engine/conflict_resolver.h',
     'engine/conflict_util.cc',
     'engine/conflict_util.h',
     'engine/download.cc',
     'engine/download.h',
     'engine/get_commit_ids.cc',
     'engine/get_commit_ids.h',
     'engine/model_changing_syncer_command.cc',
     'engine/model_changing_syncer_command.h',
@@ skipping 44 matching lines @@
     'protocol/proto_enum_conversions.h',
     'protocol/proto_value_conversions.cc',
     'protocol/proto_value_conversions.h',
     'protocol/sync_protocol_error.cc',
     'protocol/sync_protocol_error.h',
     'sessions/data_type_tracker.cc',
     'sessions/data_type_tracker.h',
     'sessions/debug_info_getter.h',
     'sessions/nudge_tracker.cc',
     'sessions/nudge_tracker.h',
-    'sessions/ordered_commit_set.cc',
-    'sessions/ordered_commit_set.h',
     'sessions/status_controller.cc',
     'sessions/status_controller.h',
     'sessions/sync_session.cc',
     'sessions/sync_session.h',
     'sessions/sync_session_context.cc',
     'sessions/sync_session_context.h',
     'syncable/blob.h',
     'syncable/dir_open_result.h',
     'syncable/directory.cc',
     'syncable/directory.h',
@@ skipping 69 matching lines @@
     'util/get_session_name_win.cc',
     'util/get_session_name_win.h',
     'util/logging.cc',
     'util/logging.h',
     'util/nigori.cc',
     'util/nigori.h',
     'util/time.cc',
     'util/time.h',
   ],
 }