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

sync/protocol/arc_package_specifics.proto

-// Copyright 2016 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.
-//
-// Sync protocol datatype extension for ARC pakcages.
-
-// Update proto_{value,enum}_conversions{.h,.cc,_unittest.cc} if you change
-// any fields in this file.
-
-syntax = "proto2";
-
-option optimize_for = LITE_RUNTIME;
-option retain_unknown_fields = true;
-
-package sync_pb;
-
-// Properties of arc package objects.
-message ArcPackageSpecifics {
-  // Unique identifier for the item:
-  // Android package name.
-  optional string package_name = 1;
-  // Android package version.
-  optional int32 package_version = 2;
-  // Last Android id generated when Android side backups data.
-  optional int64 last_backup_android_id = 3;
-  // Last time internal value that Android side backups data.
-  optional int64 last_backup_time = 4;
-}