Checkpointing some Sync Attachment work. Added SyncAttachment and SyncAttachmentId.

sync/protocol/sync.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 for communication between sync client and server.
 
 // Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
 // any fields in this file.
 
 syntax = "proto2";
@@ skipping 875 matching lines @@
     // is absent then the whole client (all datatypes) is throttled.
     repeated int32 error_data_type_ids = 5;
   }
   optional Error error = 13;
 
   // The new per-client state for this client. If set, should be persisted and
   // sent with any subsequent ClientToServerMessages.
   optional ChipBag new_bag_of_chips = 14;
 };
 
+// Identifies an attachment.
+//
+// Note, message's definition is in flux and may change. Don't rely on it.
+message SyncAttachmentId {

[Nicolas Zea, 2013/12/30 19:10:31]

Should we have this in its own proto file? This file is pretty big as is

[maniscalco, 2013/12/30 22:17:19]

Good call.  Done.  I moved it to attachments.proto.  LMK if it should be called
attachment.proto instead.

+  // Uniquely identifies the attachment. Two attachments with the same unique_id
+  // are considered equivalent.
+  optional string unique_id = 1;
+};