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

sync/protocol/article_specifics.proto

-// 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.
-//
-// Sync protocol datatype extension for the article.
-
-syntax = "proto2";
-
-option optimize_for = LITE_RUNTIME;
-option retain_unknown_fields = true;
-
-package sync_pb;
-
-import "attachments.proto";
-
-// Properties of Article objects.
-message ArticleSpecifics {
-  optional string entry_id = 1;
-
-  optional string title = 2;
-
-  repeated ArticlePage pages = 3;
-
-  optional ArticleAttachments attachments = 4;
-}
-
-message ArticlePage {
-  optional string url = 1;
-}
-
-message ArticleAttachments {
-  optional AttachmentIdProto distilled_article = 1;
-}