[Sync] Adjust UserEvent proto numbers, add Test message.

components/sync/protocol/proto_visitors.h

Index: components/sync/protocol/proto_visitors.h
diff --git a/components/sync/protocol/proto_visitors.h b/components/sync/protocol/proto_visitors.h
index 08575749cce9ae0ef76f92a252bdbb0f18cc710f..a4a96721235720a5cafc16a948a62a25878aecd3 100644
--- a/components/sync/protocol/proto_visitors.h
+++ b/components/sync/protocol/proto_visitors.h
@@ -877,11 +877,14 @@ VISIT_PROTO_FIELDS(const sync_pb::UserEventSpecifics& proto) {
   VISIT(event_time_usec);
   VISIT(navigation_id);
   VISIT(session_id);
+  VISIT(test);
   VISIT(field_trial_event);
   VISIT(language_detection);
   VISIT(translation);
 }
 
+VISIT_PROTO_FIELDS(const sync_pb::UserEventSpecifics::Test& proto) {}
+
 VISIT_PROTO_FIELDS(const sync_pb::WalletMaskedCreditCard& proto) {
   VISIT(id);
   VISIT_ENUM(status);