Update mojo sdk to rev 1dc8a9a5db73d3718d99917fadf31f5fb2ebad4f

third_party/mojo/src/mojo/public/go/bindings/decoder.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 (
         "encoding/binary"
         "fmt"
         "math"
@@ skipping 131 matching lines @@
                 return DataHeader{}, &ValidationError{UnexpectedStructHeader,
                         fmt.Sprintf("data header size(%d) should be at least %d", header.Size, dataHeaderSize),
                 }
         }
         if err := d.pushState(header, 0); err != nil {
                 return DataHeader{}, err
         }
         return header, nil
 }
 
+// StartUnion starts decoding a union and reads its header.
+// Returns the read data header. The caller should check if it is valid.
+// Note: it doesn't read the data field.
+func (d *Decoder) StartUnion() (DataHeader, error) {
+        header, err := d.readDataHeader()
+        if err != nil {
+                return DataHeader{}, err
+        }
+
+        if err := d.pushState(header, 0); err != nil {
+                return DataHeader{}, err
+        }
+        return header, nil
+}
+
 func (d *Decoder) readDataHeader() (DataHeader, error) {
         if err := d.claimData(dataHeaderSize); err != nil {
                 return DataHeader{}, err
         }
         oldEnd := d.end - dataHeaderSize
         header := DataHeader{
                 Size:              binary.LittleEndian.Uint32(d.buf[oldEnd:]),
                 ElementsOrVersion: binary.LittleEndian.Uint32(d.buf[oldEnd+4:]),
         }
         return header, nil
@@ skipping 217 matching lines @@
         handle, err := d.ReadMessagePipeHandle()
         if err != nil {
                 return nil, err
         }
         d.state().elementsProcessed--
         if _, err := d.ReadUint32(); err != nil {
                 return nil, err
         }
         return handle, nil
 }