sync: Implement per-type GetCommitIds

sync/engine/get_commit_ids.h

+// Copyright 2012 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.
+
+#ifndef SYNC_ENGINE_GET_COMMIT_IDS_H_
+#define SYNC_ENGINE_GET_COMMIT_IDS_H_
+
+#include <vector>
+
+#include "sync/base/sync_export.h"
+#include "sync/internal_api/public/base/model_type.h"
+#include "sync/syncable/directory.h"
+
+using std::vector;
+
+namespace syncer {
+
+namespace sessions {
+class OrderedCommitSet;
+}
+
+namespace syncable {
+class BaseTransaction;
+}
+
+// Returns up to |max_entries| metahandles of entries that belong to the
+// specified |type| and are ready for commit.  The returned handles will be
+// in a valid commit ordering.

[tim (not reviewing), 2013/09/08 19:48:20]

nit - Do we explain what 'valid commit ordering' is anywhere?  

+SYNC_EXPORT_PRIVATE void GetCommitIdsForType(
+    syncable::BaseTransaction* trans,
+    ModelType type,
+    size_t max_entries,
+    std::vector<int64>* out);
+
+// Fills the specified |ordered_commit_set| with up to |commit_batch_size|
+// metahandles that belong to the set of types |requested_types| and are ready
+// for commit.  The list will be in a valid commit ordering.
+SYNC_EXPORT_PRIVATE void GetCommitIds(
+    syncable::BaseTransaction* trans,
+    ModelTypeSet requested_types,
+    size_t commit_batch_size,
+    sessions::OrderedCommitSet* ordered_commit_set);
+
+}  // namespace syncer
+
+#endif  // SYNC_ENGINE_GET_COMMIT_IDS_H_