Restore the btoa/atob polyfills for Node.js

These were removed in PR 9170, since they were unused in the browsers that we'll support in PDF.js version `2.0`.
However looking at the output of Travis, where a subset of the unit-tests are run using Node.js, there's warnings about `btoa` being undefined. This doesn't appear to cause any errors, which probably explains why we didn't notice this before (despite PR 9201).

src/core/worker.js

@@ -15,11 +15,12 @@
 
 import {
   arrayByteLength, arraysToBytes, assert, createPromiseCapability, info,
-  InvalidPDFException, isNodeJS, MessageHandler, MissingPDFException,
-  PasswordException, setVerbosityLevel, UnexpectedResponseException,
-  UnknownErrorException, UNSUPPORTED_FEATURES, warn, XRefParseException
+  InvalidPDFException, MessageHandler, MissingPDFException, PasswordException,
+  setVerbosityLevel, UnexpectedResponseException, UnknownErrorException,
+  UNSUPPORTED_FEATURES, warn, XRefParseException
 } from '../shared/util';
 import { LocalPdfManager, NetworkPdfManager } from './pdf_manager';
+import isNodeJS from '../shared/is_node';
 import { Ref } from './primitives';
 
 var WorkerTask = (function WorkerTaskClosure() {

src/display/svg.js

@@ -15,10 +15,11 @@
 /* globals __non_webpack_require__ */
 
 import {
-  createObjectURL, FONT_IDENTITY_MATRIX, IDENTITY_MATRIX, ImageKind, isNodeJS,
-  isNum, OPS, Util, warn
+  createObjectURL, FONT_IDENTITY_MATRIX, IDENTITY_MATRIX, ImageKind, isNum, OPS,
+  Util, warn
 } from '../shared/util';
 import { DOMSVGFactory } from './dom_utils';
+import isNodeJS from '../shared/is_node';
 
 var SVGGraphics = function() {
   throw new Error('Not implemented: SVGGraphics');

src/pdf.js

@@ -31,7 +31,8 @@ var pdfjsDisplaySVG = require('./display/svg.js');
 
 if (typeof PDFJSDev === 'undefined' ||
     !PDFJSDev.test('FIREFOX || MOZCENTRAL')) {
-  if (pdfjsSharedUtil.isNodeJS()) {
+  const isNodeJS = require('./shared/is_node.js');
+  if (isNodeJS()) {
     var PDFNodeStream = require('./display/node_stream.js').PDFNodeStream;
     pdfjsDisplayAPI.setPDFNetworkStreamClass(PDFNodeStream);
   } else if (typeof Response !== 'undefined' && 'body' in Response.prototype &&

src/shared/compatibility.js

@@ -22,6 +22,7 @@ if ((typeof PDFJSDev === 'undefined' ||
     (typeof PDFJS === 'undefined' || !PDFJS.compatibilityChecked)) {
 
 var globalScope = require('./global_scope');
+const isNodeJS = require('./is_node');
 
 var userAgent = (typeof navigator !== 'undefined' && navigator.userAgent) || '';
 var isAndroid = /Android/.test(userAgent);
@@ -41,6 +42,28 @@ if (typeof PDFJS === 'undefined') {
 
 PDFJS.compatibilityChecked = true;
 
+// Support: Node.js
+(function checkNodeBtoa() {
+  if (globalScope.btoa || !isNodeJS()) {
+    return;
+  }
+  globalScope.btoa = function(chars) {
+    // eslint-disable-next-line no-undef
+    return Buffer.from(chars, 'binary').toString('base64');
+  };
+})();
+
+// Support: Node.js
+(function checkNodeAtob() {
+  if (globalScope.atob || !isNodeJS()) {
+    return;
+  }
+  globalScope.atob = function(input) {
+    // eslint-disable-next-line no-undef
+    return Buffer.from(input, 'base64').toString('binary');
+  };
+})();
+
 // Checks if possible to use URL.createObjectURL()
 // Support: IE, Chrome on iOS
 (function checkOnBlobSupport() {

src/shared/is_node.js

@@ -0,0 +1,19 @@
+/* Copyright 2018 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/* globals module, process */
+
+module.exports = function isNodeJS() {
+  return typeof process === 'object' && process + '' === '[object process]';
+};

src/shared/util.js

@@ -1089,11 +1089,6 @@ function isSpace(ch) {
   return (ch === 0x20 || ch === 0x09 || ch === 0x0D || ch === 0x0A);
 }
 
-function isNodeJS() {
-  // eslint-disable-next-line no-undef
-  return typeof process === 'object' && process + '' === '[object process]';
-}
-
 /**
  * Promise Capability object.
  *
@@ -1633,7 +1628,6 @@ export {
   isNum,
   isString,
   isSpace,
-  isNodeJS,
   isSameOrigin,
   createValidAbsoluteUrl,
   isLittleEndian,