Task Scheduler API migration: change BrowserThreadModelWorker to SequencedModelWorker

components/sync/engine/sequenced_model_worker.h

Index: components/sync/engine/sequenced_model_worker.h
diff --git a/components/sync/engine/sequenced_model_worker.h b/components/sync/engine/sequenced_model_worker.h
new file mode 100644
index 0000000000000000000000000000000000000000..7da1b7876e03b6f8c3250d7562c0909caf771b32
--- /dev/null
+++ b/components/sync/engine/sequenced_model_worker.h
@@ -0,0 +1,40 @@
+// 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 COMPONENTS_SYNC_ENGINE_SEQUENCED_MODEL_WORKER_H_
+#define COMPONENTS_SYNC_ENGINE_SEQUENCED_MODEL_WORKER_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/sequenced_task_runner.h"
+#include "components/sync/engine/model_safe_worker.h"
+
+namespace syncer {
+
+// A ModelSafeWorker for models that accept requests from the
+// syncapi that need to be fulfilled on a model specific sequenced task runner.
+// TODO(sync): Try to generalize other ModelWorkers (e.g. history, etc).
+class SequencedModelWorker : public ModelSafeWorker {
+ public:
+  SequencedModelWorker(const scoped_refptr<base::SequencedTaskRunner>& runner,
+                       ModelSafeGroup group);
+
+  // ModelSafeWorker implementation.
+  ModelSafeGroup GetModelSafeGroup() override;
+  bool IsOnModelSequence() override;
+
+ private:
+  ~SequencedModelWorker() override;
+
+  void ScheduleWork(base::OnceClosure work) override;
+
+  scoped_refptr<base::SequencedTaskRunner> runner_;
+  ModelSafeGroup group_;
+
+  DISALLOW_COPY_AND_ASSIGN(SequencedModelWorker);
+};
+
+}  // namespace syncer
+
+#endif  // COMPONENTS_SYNC_ENGINE_SEQUENCED_MODEL_WORKER_H_