[Sync] Create new top-level sync/ directory

chrome/browser/sync/protocol/app_notification_specifics.proto

-// 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.
-//
-// Sync protocol datatype extension for app notifications.
-
-// Update proto_value_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 an app notification.
-
-// An App Notification, to be delivered from Chrome Apps to the
-// Chrome browser through the Notification API.
-message AppNotification {
-  // Globally unique id. This is more robust for uniquely identifying each
-  // notification and hence gives us flexibility in the future. In absence
-  // of this, unique id would be (app_id, creation_timestamp_ms). But that
-  // relies on creation_timestamp_ms being high resolution and is not
-  // globally unique - only unique for a given user.
-  optional string guid = 1;
-  // Metadata, not shown directly to the user.
-  // The unique App Id, as created by the webstore and used to 
-  // delegate messages to the applications. This is defined as 32 characters
-  optional string app_id = 2;
-  // Timestamp when the message was created in milliseconds.
-  // This is seperate from ctime as this is only set by the application.
-  optional int64 creation_timestamp_ms = 3;
-
-  // Payload - these fields are visible to the user content is defined by the
-  // app. The fields are described in:
-  // chrome/browser/extensions/app_notification.h
-  optional string title = 4;
-  optional string body_text = 5;
-  optional string link_url = 6;
-  optional string link_text = 7;
-}
-