Add TextDecoder polyfill

package.json

@@ -69,6 +69,7 @@
     "istanbul": "^0.4.5",
     "mocha": "^5.0.0",
     "sinon": "^4.3.0",
+    "text-encoder-lite": "^1.0.1",
     "whatwg-fetch": "^2.0.3"
   },
   "dependencies": {

src/openpgp.js

@@ -44,15 +44,11 @@ import { CleartextMessage } from './cleartext';
 import { generate, reformat } from './key';
 import config from './config/config';
 import enums from './enums';
+import './polyfills';
 import stream from './stream';
 import util from './util';
 import AsyncProxy from './worker/async_proxy';
 
-// Old browser polyfills
-if (typeof window !== 'undefined') {
-  require('./polyfills');
-}
-
 //////////////////////////
 //                      //
 //   Web Worker setup   //

src/polyfills.js

@@ -1,8 +1,16 @@
-/* eslint-disable import/no-extraneous-dependencies */
+/**
-// Old browser polyfills
+ * @fileoverview Old browser polyfills
-// All are listed as dev dependencies because Node does not need them
+ * All are listed as dev dependencies because Node does not need them
-// and for browser babel will take care of it
+ * and for browser babel will take care of it
+ * @requires util
+ * @module polyfills
+ */
 
+import util from './util';
+
+/* eslint-disable import/no-extraneous-dependencies */
+
+if (typeof window !== 'undefined') {
   if (typeof window.fetch === 'undefined') {
     require('whatwg-fetch');
   }
@@ -31,3 +39,14 @@ if (typeof Symbol === 'undefined') {
   if (typeof Object.assign === 'undefined') {
     require('core-js/fn/object/assign');
   }
+}
+
+if (typeof TransformStream === 'undefined') {
+  require('@mattiasbuelens/web-streams-polyfill');
+}
+if (typeof TextDecoder === 'undefined') {
+  global.TextDecoder = util.getNodeTextDecoder();
+}
+if (typeof TextDecoder === 'undefined') {
+  global.TextDecoder = require('text-encoder-lite');
+}

src/stream.js

@@ -1,9 +1,5 @@
 import util from './util';
 
-if (typeof TransformStream === 'undefined') {
-  require('@mattiasbuelens/web-streams-polyfill');
-}
-
 const nodeStream = util.getNodeStream();
 
 function toStream(input) {

src/util.js

@@ -664,12 +664,19 @@ export default {
       return;
     }
 
-    // This "hack" allows us to access the native node buffer module.
-    // otherwise, it gets replaced with the browserified version
     // eslint-disable-next-line no-useless-concat, import/no-dynamic-require
     return require('stream'+'');
   },
 
+  getNodeTextDecoder: function() {
+    if (!util.detectNode()) {
+      return;
+    }
+
+    // eslint-disable-next-line no-useless-concat, import/no-dynamic-require
+    return require('util'+'').TextDecoder;
+  },
+
   isEmailAddress: function(data) {
     if (!util.isString(data)) {
       return false;