diff --git a/vendor/google.golang.org/protobuf/proto/messageset.go b/vendor/google.golang.org/protobuf/proto/messageset.go
new file mode 100644
index 0000000..312d5d4
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/proto/messageset.go
@@ -0,0 +1,93 @@
+// Copyright 2019 The Go 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 proto
+
+import (
+	"google.golang.org/protobuf/encoding/protowire"
+	"google.golang.org/protobuf/internal/encoding/messageset"
+	"google.golang.org/protobuf/internal/errors"
+	"google.golang.org/protobuf/internal/flags"
+	"google.golang.org/protobuf/internal/order"
+	"google.golang.org/protobuf/reflect/protoreflect"
+	"google.golang.org/protobuf/reflect/protoregistry"
+)
+
+func (o MarshalOptions) sizeMessageSet(m protoreflect.Message) (size int) {
+	m.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
+		size += messageset.SizeField(fd.Number())
+		size += protowire.SizeTag(messageset.FieldMessage)
+		size += protowire.SizeBytes(o.size(v.Message()))
+		return true
+	})
+	size += messageset.SizeUnknown(m.GetUnknown())
+	return size
+}
+
+func (o MarshalOptions) marshalMessageSet(b []byte, m protoreflect.Message) ([]byte, error) {
+	if !flags.ProtoLegacy {
+		return b, errors.New("no support for message_set_wire_format")
+	}
+	fieldOrder := order.AnyFieldOrder
+	if o.Deterministic {
+		fieldOrder = order.NumberFieldOrder
+	}
+	var err error
+	order.RangeFields(m, fieldOrder, func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
+		b, err = o.marshalMessageSetField(b, fd, v)
+		return err == nil
+	})
+	if err != nil {
+		return b, err
+	}
+	return messageset.AppendUnknown(b, m.GetUnknown())
+}
+
+func (o MarshalOptions) marshalMessageSetField(b []byte, fd protoreflect.FieldDescriptor, value protoreflect.Value) ([]byte, error) {
+	b = messageset.AppendFieldStart(b, fd.Number())
+	b = protowire.AppendTag(b, messageset.FieldMessage, protowire.BytesType)
+	b = protowire.AppendVarint(b, uint64(o.Size(value.Message().Interface())))
+	b, err := o.marshalMessage(b, value.Message())
+	if err != nil {
+		return b, err
+	}
+	b = messageset.AppendFieldEnd(b)
+	return b, nil
+}
+
+func (o UnmarshalOptions) unmarshalMessageSet(b []byte, m protoreflect.Message) error {
+	if !flags.ProtoLegacy {
+		return errors.New("no support for message_set_wire_format")
+	}
+	return messageset.Unmarshal(b, false, func(num protowire.Number, v []byte) error {
+		err := o.unmarshalMessageSetField(m, num, v)
+		if err == errUnknown {
+			unknown := m.GetUnknown()
+			unknown = protowire.AppendTag(unknown, num, protowire.BytesType)
+			unknown = protowire.AppendBytes(unknown, v)
+			m.SetUnknown(unknown)
+			return nil
+		}
+		return err
+	})
+}
+
+func (o UnmarshalOptions) unmarshalMessageSetField(m protoreflect.Message, num protowire.Number, v []byte) error {
+	md := m.Descriptor()
+	if !md.ExtensionRanges().Has(num) {
+		return errUnknown
+	}
+	xt, err := o.Resolver.FindExtensionByNumber(md.FullName(), num)
+	if err == protoregistry.NotFound {
+		return errUnknown
+	}
+	if err != nil {
+		return errors.New("%v: unable to resolve extension %v: %v", md.FullName(), num, err)
+	}
+	xd := xt.TypeDescriptor()
+	if err := o.unmarshalMessage(v, m.Mutable(xd).Message()); err != nil {
+		return err
+	}
+	return nil
+}