sync: Add non-blocking type encryption (retry)

sync/internal_api/public/non_blocking_sync_common.h

 // Copyright 2014 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_INTERNAL_API_PUBLIC_NON_BLOCKING_SYNC_COMMON_H_
 #define SYNC_INTERNAL_API_PUBLIC_NON_BLOCKING_SYNC_COMMON_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 20 matching lines @@
   // be data-type specific.  Many data types ignore it.
   sync_pb::DataTypeContext type_context;
 
   // The ID of the folder node that sits at the top of this type's folder
   // hierarchy.  We keep this around for legacy reasons.  The protocol expects
   // that all nodes of a certain type are children of the same type root
   // entity.  This entity is delivered by the server, and may not be available
   // until the first download cycle has completed.
   std::string type_root_id;
 
+  // This value is set if this type's data should be encrypted on the server.
+  // If this key changes, the client will need to re-commit all of its local
+  // data to the server using the new encryption key.
+  std::string encryption_key_name;
+
   // A strictly increasing counter used to generate unique values for the
   // client-assigned IDs.  The incrementing and ID assignment happens on the
   // sync thread, but we store the value here so we can pass it back to the
   // model thread for persistence.  This is probably unnecessary for the
   // client-tagged data types supported by non-blocking sync, but we will
   // continue to emulate the directory sync's behavior for now.
   int64 next_client_id;
 
   // This flag is set to true when the first download cycle is complete.  The
   // ModelTypeSyncProxy should not attempt to commit any items until this
   // flag is set.
   bool initial_sync_done;
 };
-
 struct SYNC_EXPORT_PRIVATE CommitRequestData {
   CommitRequestData();
   ~CommitRequestData();
 
   std::string id;
   std::string client_tag_hash;
 
   // Strictly incrementing number for in-progress commits.  More information
   // about its meaning can be found in comments in the files that make use of
   // this struct.
@@ skipping 22 matching lines @@
   ~UpdateResponseData();
 
   std::string id;
   std::string client_tag_hash;
   int64 response_version;
   base::Time ctime;
   base::Time mtime;
   std::string non_unique_name;
   bool deleted;
   sync_pb::EntitySpecifics specifics;
+  std::string encryption_key_name;
 };
 
 typedef std::vector<CommitRequestData> CommitRequestDataList;
 typedef std::vector<CommitResponseData> CommitResponseDataList;
 typedef std::vector<UpdateResponseData> UpdateResponseDataList;
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_NON_BLOCKING_SYNC_COMMON_H_