[Sync] Move //sync to //components/sync.

sync/engine/nudge_source.h

-// Copyright (c) 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_NUDGE_SOURCE_H_
-#define SYNC_ENGINE_NUDGE_SOURCE_H_
-
-namespace syncer {
-
-enum NudgeSource {
-  NUDGE_SOURCE_UNKNOWN = 0,
-  // We received an invalidation message and are nudging to check for updates.
-  NUDGE_SOURCE_NOTIFICATION,
-  // A local change occurred (e.g. bookmark moved).
-  NUDGE_SOURCE_LOCAL,
-  // A local event is triggering an optimistic datatype refresh.
-  NUDGE_SOURCE_LOCAL_REFRESH,
-};
-
-const char* GetNudgeSourceString(NudgeSource nudge_source);
-
-}  // namespace syncer
-
-#endif  // SYNC_ENGINE_NUDGE_SOURCE_H_