[Sync] Add size and crc32c to AttachmentId.

sync/api/attachments/attachment_id.cc

Index: sync/api/attachments/attachment_id.cc
diff --git a/sync/api/attachments/attachment_id.cc b/sync/api/attachments/attachment_id.cc
index e61705e63ab7daecd4456249790e5bd17b159045..07f34102021517532a8079928b9fc2e91afc70d1 100644
--- a/sync/api/attachments/attachment_id.cc
+++ b/sync/api/attachments/attachment_id.cc
@@ -52,8 +52,8 @@ bool AttachmentId::operator<(const AttachmentId& other) const {
 }
 
 // Static.
-AttachmentId AttachmentId::Create() {
-  sync_pb::AttachmentIdProto proto = CreateAttachmentIdProto();
+AttachmentId AttachmentId::Create(size_t size, uint32_t crc32c) {
+  sync_pb::AttachmentIdProto proto = CreateAttachmentIdProto(size, crc32c);
   return AttachmentId(&proto);
 }
 
@@ -71,4 +71,12 @@ const sync_pb::AttachmentIdProto& AttachmentId::GetProto() const {
 AttachmentId::AttachmentId(sync_pb::AttachmentIdProto* proto)
     : proto_(proto) {}
 
+size_t AttachmentId::GetSize() const {
+  return proto_.Get().size_bytes();
+}
+
+uint32_t AttachmentId::GetCrc32c() const {
+  return proto_.Get().crc32c();
+}
+
 }  // namespace syncer