go/bindings: update code to pass structs versions tests

mojo/public/go/bindings/message.go

 // Copyright 2015 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.
 
 package bindings
 
 import (
         "fmt"
 
         "mojo/public/go/system"
@@ skipping 50 matching lines @@
         }
         if h.RequestId != 0 {
                 if err := encoder.WriteUint64(h.RequestId); err != nil {
                         return err
                 }
         }
         return encoder.Finish()
 }
 
 func (h *MessageHeader) Decode(decoder *Decoder) error {
-        numFields, err := decoder.StartStruct()
+        header, err := decoder.StartStruct()
         if err != nil {
                 return err
         }
+        numFields := header.ElementsOrVersion
         if numFields < 2 || numFields > 3 {
                 return fmt.Errorf("Invalid message header: it should have 2 or 3 fileds, but has %d", numFields)
         }
         if h.Type, err = decoder.ReadUint32(); err != nil {
                 return err
         }
         if h.Flags, err = decoder.ReadUint32(); err != nil {
                 return err
         }
         if numFields == 3 {
@@ skipping 70 matching lines @@
 // ParseMessage parses message header from byte buffer with attached handles
 // and returnes parsed message.
 func ParseMessage(bytes []byte, handles []system.UntypedHandle) (*Message, error) {
         decoder := NewDecoder(bytes, []system.UntypedHandle{})
         var header MessageHeader
         if err := header.Decode(decoder); err != nil {
                 return nil, err
         }
         return newMessage(header, bytes, handles), nil
 }