[Sync] Create new top-level sync/ directory

chrome/browser/sync/protocol/encryption.proto

-// Copyright (c) 2010 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.
-//
-// Common sync protocol for encrypted data.
-
-// 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;
-
-// Encrypted sync data consists of two parts: a key name and a blob. Key name is
-// the name of the key that was used to encrypt blob and blob is encrypted data
-// itself.
-//
-// The reason we need to keep track of the key name is that a sync user can
-// change their passphrase (and thus their encryption key) at any time. When
-// that happens, we make a best effort to reencrypt all nodes with the new
-// passphrase, but since we don't have transactions on the server-side, we
-// cannot guarantee that every node will be reencrypted. As a workaround, we
-// keep track of all keys, assign each key a name (by using that key to encrypt
-// a well known string) and keep track of which key was used to encrypt each
-// node.
-message EncryptedData {
-  optional string key_name = 1;
-  optional string blob = 2;
-};