sync: Add interfaces for per-type sync

sync/engine/sync_directory_commit_contributor.cc

Index: sync/engine/sync_directory_commit_contributor.cc
diff --git a/sync/engine/sync_directory_commit_contributor.cc b/sync/engine/sync_directory_commit_contributor.cc
deleted file mode 100644
index c87c8eda8706462b721ca7119f563cd360efb6c6..0000000000000000000000000000000000000000
--- a/sync/engine/sync_directory_commit_contributor.cc
+++ /dev/null
@@ -1,24 +0,0 @@
-// 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 "sync/engine/sync_directory_commit_contributor.h"
-
-#include "sync/engine/sync_directory_commit_contribution.h"
-
-namespace syncer {
-
-SyncDirectoryCommitContributor::SyncDirectoryCommitContributor(
-    syncable::Directory* dir,
-    ModelType type)
-    : dir_(dir),
-      type_(type) {}
-
-SyncDirectoryCommitContributor::~SyncDirectoryCommitContributor() {}
-
-SyncDirectoryCommitContribution*
-SyncDirectoryCommitContributor::GetContribution(size_t max_entries) {
-  return SyncDirectoryCommitContribution::Build(dir_, type_, max_entries);
-}
-
-}  // namespace syncer