diff --git a/vendor/google.golang.org/protobuf/internal/encoding/text/decode_string.go b/vendor/google.golang.org/protobuf/internal/encoding/text/decode_string.go
new file mode 100644
index 0000000..d4d3490
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/encoding/text/decode_string.go
@@ -0,0 +1,161 @@
+// Copyright 2018 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 text
+
+import (
+	"bytes"
+	"strconv"
+	"strings"
+	"unicode"
+	"unicode/utf16"
+	"unicode/utf8"
+
+	"google.golang.org/protobuf/internal/strs"
+)
+
+// parseStringValue parses string field token.
+// This differs from parseString since the text format allows
+// multiple back-to-back string literals where they are semantically treated
+// as a single large string with all values concatenated.
+//
+// E.g., `"foo" "bar" "baz"` => "foobarbaz"
+func (d *Decoder) parseStringValue() (Token, error) {
+	// Note that the ending quote is sufficient to unambiguously mark the end
+	// of a string. Thus, the text grammar does not require intervening
+	// whitespace or control characters in-between strings.
+	// Thus, the following is valid:
+	//	`"foo"'bar'"baz"` => "foobarbaz"
+	in0 := d.in
+	var ss []string
+	for len(d.in) > 0 && (d.in[0] == '"' || d.in[0] == '\'') {
+		s, err := d.parseString()
+		if err != nil {
+			return Token{}, err
+		}
+		ss = append(ss, s)
+	}
+	// d.in already points to the end of the value at this point.
+	return Token{
+		kind:  Scalar,
+		attrs: stringValue,
+		pos:   len(d.orig) - len(in0),
+		raw:   in0[:len(in0)-len(d.in)],
+		str:   strings.Join(ss, ""),
+	}, nil
+}
+
+// parseString parses a string value enclosed in " or '.
+func (d *Decoder) parseString() (string, error) {
+	in := d.in
+	if len(in) == 0 {
+		return "", ErrUnexpectedEOF
+	}
+	quote := in[0]
+	in = in[1:]
+	i := indexNeedEscapeInBytes(in)
+	in, out := in[i:], in[:i:i] // set cap to prevent mutations
+	for len(in) > 0 {
+		switch r, n := utf8.DecodeRune(in); {
+		case r == utf8.RuneError && n == 1:
+			return "", d.newSyntaxError("invalid UTF-8 detected")
+		case r == 0 || r == '\n':
+			return "", d.newSyntaxError("invalid character %q in string", r)
+		case r == rune(quote):
+			in = in[1:]
+			d.consume(len(d.in) - len(in))
+			return string(out), nil
+		case r == '\\':
+			if len(in) < 2 {
+				return "", ErrUnexpectedEOF
+			}
+			switch r := in[1]; r {
+			case '"', '\'', '\\', '?':
+				in, out = in[2:], append(out, r)
+			case 'a':
+				in, out = in[2:], append(out, '\a')
+			case 'b':
+				in, out = in[2:], append(out, '\b')
+			case 'n':
+				in, out = in[2:], append(out, '\n')
+			case 'r':
+				in, out = in[2:], append(out, '\r')
+			case 't':
+				in, out = in[2:], append(out, '\t')
+			case 'v':
+				in, out = in[2:], append(out, '\v')
+			case 'f':
+				in, out = in[2:], append(out, '\f')
+			case '0', '1', '2', '3', '4', '5', '6', '7':
+				// One, two, or three octal characters.
+				n := len(in[1:]) - len(bytes.TrimLeft(in[1:], "01234567"))
+				if n > 3 {
+					n = 3
+				}
+				v, err := strconv.ParseUint(string(in[1:1+n]), 8, 8)
+				if err != nil {
+					return "", d.newSyntaxError("invalid octal escape code %q in string", in[:1+n])
+				}
+				in, out = in[1+n:], append(out, byte(v))
+			case 'x':
+				// One or two hexadecimal characters.
+				n := len(in[2:]) - len(bytes.TrimLeft(in[2:], "0123456789abcdefABCDEF"))
+				if n > 2 {
+					n = 2
+				}
+				v, err := strconv.ParseUint(string(in[2:2+n]), 16, 8)
+				if err != nil {
+					return "", d.newSyntaxError("invalid hex escape code %q in string", in[:2+n])
+				}
+				in, out = in[2+n:], append(out, byte(v))
+			case 'u', 'U':
+				// Four or eight hexadecimal characters
+				n := 6
+				if r == 'U' {
+					n = 10
+				}
+				if len(in) < n {
+					return "", ErrUnexpectedEOF
+				}
+				v, err := strconv.ParseUint(string(in[2:n]), 16, 32)
+				if utf8.MaxRune < v || err != nil {
+					return "", d.newSyntaxError("invalid Unicode escape code %q in string", in[:n])
+				}
+				in = in[n:]
+
+				r := rune(v)
+				if utf16.IsSurrogate(r) {
+					if len(in) < 6 {
+						return "", ErrUnexpectedEOF
+					}
+					v, err := strconv.ParseUint(string(in[2:6]), 16, 16)
+					r = utf16.DecodeRune(r, rune(v))
+					if in[0] != '\\' || in[1] != 'u' || r == unicode.ReplacementChar || err != nil {
+						return "", d.newSyntaxError("invalid Unicode escape code %q in string", in[:6])
+					}
+					in = in[6:]
+				}
+				out = append(out, string(r)...)
+			default:
+				return "", d.newSyntaxError("invalid escape code %q in string", in[:2])
+			}
+		default:
+			i := indexNeedEscapeInBytes(in[n:])
+			in, out = in[n+i:], append(out, in[:n+i]...)
+		}
+	}
+	return "", ErrUnexpectedEOF
+}
+
+// indexNeedEscapeInString returns the index of the character that needs
+// escaping. If no characters need escaping, this returns the input length.
+func indexNeedEscapeInBytes(b []byte) int { return indexNeedEscapeInString(strs.UnsafeString(b)) }
+
+// UnmarshalString returns an unescaped string given a textproto string value.
+// String value needs to contain single or double quotes. This is only used by
+// internal/encoding/defval package for unmarshaling bytes.
+func UnmarshalString(s string) (string, error) {
+	d := NewDecoder([]byte(s))
+	return d.parseString()
+}