From c56f3f04dd253cc29a24c654e3caa58ae387a140 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Wed, 17 Jan 2018 18:20:00 +0100
Subject: [PATCH 1/4] [api-major] Remove the `SINGLE_FILE` build target

Please note that this build target, and the resulting `build/pdf.combined.js` file, is equivalent to setting the `PDFJS.disableWorker` option to `true` which is a performance footgun.
---
 gulpfile.js        | 27 +--------------------------
 src/display/api.js | 12 +++---------
 src/display/svg.js |  3 +--
 src/pdf.js         |  5 ++---
 4 files changed, 7 insertions(+), 40 deletions(-)

diff --git a/gulpfile.js b/gulpfile.js
index 8300332095466..4d2bdc808d7b3 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -48,7 +48,6 @@ var BASELINE_DIR = BUILD_DIR + 'baseline/';
 var MOZCENTRAL_BASELINE_DIR = BUILD_DIR + 'mozcentral.baseline/';
 var GENERIC_DIR = BUILD_DIR + 'generic/';
 var COMPONENTS_DIR = BUILD_DIR + 'components/';
-var SINGLE_FILE_DIR = BUILD_DIR + 'singlefile/';
 var MINIFIED_DIR = BUILD_DIR + 'minified/';
 var FIREFOX_BUILD_DIR = BUILD_DIR + 'firefox/';
 var CHROME_BUILD_DIR = BUILD_DIR + 'chromium/';
@@ -79,7 +78,6 @@ var DEFINES = {
   MOZCENTRAL: false,
   CHROME: false,
   MINIFIED: false,
-  SINGLE_FILE: false,
   COMPONENTS: false,
   LIB: false,
   SKIP_BABEL: false,
@@ -235,10 +233,6 @@ function createBundle(defines) {
 
   var mainAMDName = 'pdfjs-dist/build/pdf';
   var mainOutputName = 'pdf.js';
-  if (defines.SINGLE_FILE) {
-    mainAMDName = 'pdfjs-dist/build/pdf.combined';
-    mainOutputName = 'pdf.combined.js';
-  }
 
   var mainFileConfig = createWebpackConfig(defines, {
     filename: mainOutputName,
@@ -250,9 +244,6 @@ function createBundle(defines) {
     .pipe(webpack2Stream(mainFileConfig))
     .pipe(replaceWebpackRequire())
     .pipe(replaceJSRootName(mainAMDName));
-  if (defines.SINGLE_FILE) {
-    return mainOutput; // don't need a worker file.
-  }
 
   var workerAMDName = 'pdfjs-dist/build/pdf.worker';
   var workerOutputName = 'pdf.worker.js';
@@ -634,18 +625,6 @@ gulp.task('components', ['buildnumber'], function () {
   ]);
 });
 
-gulp.task('singlefile', ['buildnumber'], function () {
-  console.log();
-  console.log('### Creating singlefile build');
-  var defines = builder.merge(DEFINES, { SINGLE_FILE: true, });
-
-  var SINGLE_FILE_BUILD_DIR = SINGLE_FILE_DIR + 'build/';
-
-  rimraf.sync(SINGLE_FILE_DIR);
-
-  return createBundle(defines).pipe(gulp.dest(SINGLE_FILE_BUILD_DIR));
-});
-
 gulp.task('minified-pre', ['buildnumber', 'locale'], function () {
   console.log();
   console.log('### Creating minified viewer');
@@ -1275,9 +1254,7 @@ gulp.task('gh-pages-git', ['gh-pages-prepare', 'wintersmith'], function () {
 
 gulp.task('web', ['gh-pages-prepare', 'wintersmith', 'gh-pages-git']);
 
-gulp.task('dist-pre',
-          ['generic', 'singlefile', 'components', 'lib', 'minified'],
-          function () {
+gulp.task('dist-pre', ['generic', 'components', 'lib', 'minified'], function() {
   var VERSION = getVersionJSON().version;
 
   console.log();
@@ -1359,8 +1336,6 @@ gulp.task('dist-pre',
       GENERIC_DIR + 'build/pdf.js.map',
       GENERIC_DIR + 'build/pdf.worker.js',
       GENERIC_DIR + 'build/pdf.worker.js.map',
-      SINGLE_FILE_DIR + 'build/pdf.combined.js',
-      SINGLE_FILE_DIR + 'build/pdf.combined.js.map',
       SRC_DIR + 'pdf.worker.entry.js',
     ]).pipe(gulp.dest(DIST_DIR + 'build/')),
     gulp.src(MINIFIED_DIR + 'build/pdf.js')
diff --git a/src/display/api.js b/src/display/api.js
index d70014d73a693..d53e9db3e546b 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -46,8 +46,7 @@ var pdfjsFilePath =
 
 var fakeWorkerFilesLoader = null;
 var useRequireEnsure = false;
-if (typeof PDFJSDev !== 'undefined' &&
-    PDFJSDev.test('GENERIC && !SINGLE_FILE')) {
+if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('GENERIC')) {
   // For GENERIC build we need add support of different fake file loaders
   // for different  frameworks.
   if (typeof window === 'undefined') {
@@ -1243,10 +1242,6 @@ var PDFWorker = (function PDFWorkerClosure() {
         throw new Error(
           'SystemJS or CommonJS must be used to load fake worker.');
       }
-    } else if (PDFJSDev.test('SINGLE_FILE')) {
-      var pdfjsCoreWorker = require('../core/worker.js');
-      WorkerMessageHandler = pdfjsCoreWorker.WorkerMessageHandler;
-      fakeWorkerFilesLoadedCapability.resolve(WorkerMessageHandler);
     } else {
       var loader = fakeWorkerFilesLoader || function (callback) {
         Util.loadScript(getWorkerSrc(), function () {
@@ -1320,9 +1315,8 @@ var PDFWorker = (function PDFWorkerClosure() {
       // all requirements to run parts of pdf.js in a web worker.
       // Right now, the requirement is, that an Uint8Array is still an
       // Uint8Array as it arrives on the worker. (Chrome added this with v.15.)
-      if ((typeof PDFJSDev === 'undefined' || !PDFJSDev.test('SINGLE_FILE')) &&
-          !isWorkerDisabled && !getDefaultSetting('disableWorker') &&
-          typeof Worker !== 'undefined') {
+      if (typeof Worker !== 'undefined' && !isWorkerDisabled &&
+          !getDefaultSetting('disableWorker')) {
         var workerSrc = getWorkerSrc();
 
         try {
diff --git a/src/display/svg.js b/src/display/svg.js
index 1322114b28f34..a9a7a0ca92c62 100644
--- a/src/display/svg.js
+++ b/src/display/svg.js
@@ -25,8 +25,7 @@ var SVGGraphics = function() {
   throw new Error('Not implemented: SVGGraphics');
 };
 
-if (typeof PDFJSDev === 'undefined' ||
-    PDFJSDev.test('GENERIC || SINGLE_FILE')) {
+if (typeof PDFJSDev === 'undefined' || PDFJSDev.test('GENERIC')) {
 
 var SVG_DEFAULTS = {
   fontStyle: 'normal',
diff --git a/src/pdf.js b/src/pdf.js
index 8ef2263dce644..38e5e458ca280 100644
--- a/src/pdf.js
+++ b/src/pdf.js
@@ -29,8 +29,7 @@ var pdfjsDisplayAnnotationLayer = require('./display/annotation_layer.js');
 var pdfjsDisplayDOMUtils = require('./display/dom_utils.js');
 var pdfjsDisplaySVG = require('./display/svg.js');
 
-if (typeof PDFJSDev === 'undefined' ||
-    !PDFJSDev.test('FIREFOX || MOZCENTRAL || CHROME')) {
+if (typeof PDFJSDev === 'undefined' || PDFJSDev.test('GENERIC')) {
   const isNodeJS = require('./shared/is_node.js');
   if (isNodeJS()) {
     let PDFNodeStream = require('./display/node_stream.js').PDFNodeStream;
@@ -43,7 +42,7 @@ if (typeof PDFJSDev === 'undefined' ||
     pdfjsDisplayAPI.setPDFNetworkStreamFactory((params) => {
       return new PDFFetchStream(params);
     });
-   } else {
+  } else {
     let PDFNetworkStream = require('./display/network.js').PDFNetworkStream;
     pdfjsDisplayAPI.setPDFNetworkStreamFactory((params) => {
       return new PDFNetworkStream(params);

From a5aaf627540c5c4cae618503573419717e97db9a Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Mon, 29 Jan 2018 15:58:40 +0100
Subject: [PATCH 2/4] [api-minor] Add a (static) `PDFWorker.getWorkerSrc`
 method that returns the current `workerSrc`

This method returns the currently used `workerSrc`, which thus allows obtaining the fallback `workerSrc` value (e.g. when the option wasn't set by the user).
---
 src/display/api.js    | 4 ++++
 test/unit/api_spec.js | 7 ++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/display/api.js b/src/display/api.js
index d53e9db3e546b..afc08c047dab0 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -1485,6 +1485,10 @@ var PDFWorker = (function PDFWorkerClosure() {
     return new PDFWorker(null, port);
   };
 
+  PDFWorker.getWorkerSrc = function() {
+    return getWorkerSrc();
+  };
+
   return PDFWorker;
 })();
 
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index 04e543bdf919b..955200effd477 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -24,7 +24,7 @@ import {
   DOMCanvasFactory, RenderingCancelledException
 } from '../../src/display/dom_utils';
 import {
-  getDocument, PDFDocumentProxy, PDFPageProxy
+  getDocument, PDFDocumentProxy, PDFPageProxy, PDFWorker
 } from '../../src/display/api';
 import isNodeJS from '../../src/shared/is_node';
 import { PDFJS } from '../../src/display/global';
@@ -405,6 +405,11 @@ describe('api', function() {
         done.fail(reason);
       });
     });
+    it('gets current workerSrc', function() {
+      let workerSrc = PDFWorker.getWorkerSrc();
+      expect(typeof workerSrc).toEqual('string');
+      expect(workerSrc).toEqual(PDFJS.workerSrc);
+    });
   });
   describe('PDFDocument', function() {
     var loadingTask;

From 56a8c934dde6cce806b1d74fa80c181eb30bbb96 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 19 Jan 2018 18:16:17 +0100
Subject: [PATCH 3/4] [api-major] Remove the `PDFJS.disableWorker` option

Despite this patch removing the `disableWorker` option itself, please note that we'll still fallback to loading the worker file(s) on the main-thread when running in environments without proper Web Worker support.

Furthermore it's still possible, even with this patch, to force the use of fake workers by manually loading the necessary file using a `<script>` tag on the main-thread.[1]
That way, the functionality of the now removed `SINGLE_FILE` build target and the resulting `build/pdf.combined.js` file can still be achieved simply by adding e.g. `<script src="build/pdf.worker.js"></script>` to the HTML (obviously with the path adjusted as needed).

Finally note that the `disableWorker` option is a performance footgun, and unfortunately many existing third-party examples actually use it without providing any sort of warning/justification.

---

[1] This approach is used in the default viewer, since certain kind of debugging may be easier if the code is running directly on the main-thread.
---
 examples/browserify/main.js         |  3 ---
 examples/learning/helloworld.html   |  7 ------
 examples/learning/helloworld64.html |  6 -----
 examples/learning/prevnext.html     |  8 ------
 examples/webpack/main.js            |  3 ---
 external/dist/webpack.js            |  2 --
 src/display/api.js                  | 24 ++++++++++++++++--
 src/display/dom_utils.js            |  2 --
 src/display/global.js               | 12 +--------
 test/unit/api_spec.js               | 16 ++++++------
 web/app.js                          | 38 ++++++++++++++++++++++++++---
 11 files changed, 64 insertions(+), 57 deletions(-)

diff --git a/examples/browserify/main.js b/examples/browserify/main.js
index 46a921a591863..42c640ef09027 100644
--- a/examples/browserify/main.js
+++ b/examples/browserify/main.js
@@ -10,9 +10,6 @@ var pdfPath = '../helloworld/helloworld.pdf';
 // Setting worker path to worker bundle.
 PDFJS.workerSrc = '../../build/browserify/pdf.worker.bundle.js';
 
-// It is also possible to disable workers via `PDFJS.disableWorker = true`,
-// however that might degrade the UI performance in web browsers.
-
 // Loading a document.
 var loadingTask = PDFJS.getDocument(pdfPath);
 loadingTask.promise.then(function (pdfDocument) {
diff --git a/examples/learning/helloworld.html b/examples/learning/helloworld.html
index 4142ef6f5a81e..c2988c28707a4 100644
--- a/examples/learning/helloworld.html
+++ b/examples/learning/helloworld.html
@@ -19,13 +19,6 @@ <h1>'Hello, world!' example</h1>
   //
   var url = './helloworld.pdf';
 
-  //
-  // Disable workers to avoid yet another cross-origin issue (workers need
-  // the URL of the script to be loaded, and dynamically loading a cross-origin
-  // script does not work).
-  //
-  // PDFJS.disableWorker = true;
-
   //
   // The workerSrc property shall be specified.
   //
diff --git a/examples/learning/helloworld64.html b/examples/learning/helloworld64.html
index 58890fe87a065..69420495a5340 100644
--- a/examples/learning/helloworld64.html
+++ b/examples/learning/helloworld64.html
@@ -31,12 +31,6 @@ <h1>'Hello, world!' example</h1>
     'MDAwIG4gCjAwMDAwMDAzODAgMDAwMDAgbiAKdHJhaWxlcgo8PAogIC9TaXplIDYKICAvUm9v' +
     'dCAxIDAgUgo+PgpzdGFydHhyZWYKNDkyCiUlRU9G');
 
-  // Disable workers to avoid yet another cross-origin issue (workers need
-  // the URL of the script to be loaded, and dynamically loading a cross-origin
-  // script does not work).
-  //
-  // PDFJS.disableWorker = true;
-
   //
   // The workerSrc property shall be specified.
   //
diff --git a/examples/learning/prevnext.html b/examples/learning/prevnext.html
index 463527a3df1bb..f7e68f2b5d42d 100644
--- a/examples/learning/prevnext.html
+++ b/examples/learning/prevnext.html
@@ -28,14 +28,6 @@ <h1>'Previous/Next' example</h1>
   //
   var url = '../../web/compressed.tracemonkey-pldi-09.pdf';
 
-
-  //
-  // Disable workers to avoid yet another cross-origin issue (workers need
-  // the URL of the script to be loaded, and dynamically loading a cross-origin
-  // script does not work).
-  //
-  // PDFJS.disableWorker = true;
-
   //
   // In cases when the pdf.worker.js is located at the different folder than the
   // pdf.js's one, or the pdf.js is executed via eval(), the workerSrc property
diff --git a/examples/webpack/main.js b/examples/webpack/main.js
index d0466b86d79d8..d1beb101cb1a4 100644
--- a/examples/webpack/main.js
+++ b/examples/webpack/main.js
@@ -10,9 +10,6 @@ var pdfPath = '../helloworld/helloworld.pdf';
 // Setting worker path to worker bundle.
 pdfjsLib.PDFJS.workerSrc = '../../build/webpack/pdf.worker.bundle.js';
 
-// It is also possible to disable workers via `PDFJS.disableWorker = true`,
-// however that might degrade the UI performance in web browsers.
-
 // Loading a document.
 var loadingTask = pdfjsLib.getDocument(pdfPath);
 loadingTask.promise.then(function (pdfDocument) {
diff --git a/external/dist/webpack.js b/external/dist/webpack.js
index f2c4a6400898c..af397943940ea 100644
--- a/external/dist/webpack.js
+++ b/external/dist/webpack.js
@@ -19,8 +19,6 @@ var PdfjsWorker = require('worker-loader!./build/pdf.worker.js');
 
 if (typeof window !== 'undefined' && 'Worker' in window) {
   pdfjs.PDFJS.workerPort = new PdfjsWorker();
-} else {
-  pdfjs.PDFJS.disableWorker = true;
 }
 
 module.exports = pdfjs;
diff --git a/src/display/api.js b/src/display/api.js
index afc08c047dab0..c62c3e7c1bca2 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -1216,6 +1216,19 @@ var PDFWorker = (function PDFWorkerClosure() {
     throw new Error('No PDFJS.workerSrc specified');
   }
 
+  function getMainThreadWorkerMessageHandler() {
+    if (typeof window === 'undefined') {
+      return null;
+    }
+    if (typeof PDFJSDev === 'undefined' || !PDFJSDev.test('PRODUCTION')) {
+      return (window.pdfjsNonProductionPdfWorker &&
+              window.pdfjsNonProductionPdfWorker.WorkerMessageHandler);
+    }
+    // PRODUCTION
+    return (window.pdfjsDistBuildPdfWorker &&
+            window.pdfjsDistBuildPdfWorker.WorkerMessageHandler);
+  }
+
   let fakeWorkerFilesLoadedCapability;
 
   // Loads worker code into main thread.
@@ -1225,6 +1238,13 @@ var PDFWorker = (function PDFWorkerClosure() {
       return fakeWorkerFilesLoadedCapability.promise;
     }
     fakeWorkerFilesLoadedCapability = createPromiseCapability();
+
+    let mainWorkerMessageHandler = getMainThreadWorkerMessageHandler();
+    if (mainWorkerMessageHandler) {
+      // The worker was already loaded using a `<script>` tag.
+      fakeWorkerFilesLoadedCapability.resolve(mainWorkerMessageHandler);
+      return fakeWorkerFilesLoadedCapability.promise;
+    }
     // In the developer build load worker_loader which in turn loads all the
     // other files and resolves the promise. In production only the
     // pdf.worker.js file is needed.
@@ -1316,7 +1336,7 @@ var PDFWorker = (function PDFWorkerClosure() {
       // Right now, the requirement is, that an Uint8Array is still an
       // Uint8Array as it arrives on the worker. (Chrome added this with v.15.)
       if (typeof Worker !== 'undefined' && !isWorkerDisabled &&
-          !getDefaultSetting('disableWorker')) {
+          !getMainThreadWorkerMessageHandler()) {
         var workerSrc = getWorkerSrc();
 
         try {
@@ -1427,7 +1447,7 @@ var PDFWorker = (function PDFWorkerClosure() {
     },
 
     _setupFakeWorker: function PDFWorker_setupFakeWorker() {
-      if (!isWorkerDisabled && !getDefaultSetting('disableWorker')) {
+      if (!isWorkerDisabled) {
         warn('Setting up fake worker.');
         isWorkerDisabled = true;
       }
diff --git a/src/display/dom_utils.js b/src/display/dom_utils.js
index 442d163e037e4..e8c0d28a988df 100644
--- a/src/display/dom_utils.js
+++ b/src/display/dom_utils.js
@@ -361,8 +361,6 @@ function getDefaultSetting(id) {
       return globalSettings ? globalSettings.workerPort : null;
     case 'workerSrc':
       return globalSettings ? globalSettings.workerSrc : null;
-    case 'disableWorker':
-      return globalSettings ? globalSettings.disableWorker : false;
     case 'maxImageSize':
       return globalSettings ? globalSettings.maxImageSize : -1;
     case 'imageResourcesPath':
diff --git a/src/display/global.js b/src/display/global.js
index 885781cd699a4..b6be094824ba3 100644
--- a/src/display/global.js
+++ b/src/display/global.js
@@ -128,15 +128,6 @@ PDFJS.disableFontFace = (PDFJS.disableFontFace === undefined ?
 PDFJS.imageResourcesPath = (PDFJS.imageResourcesPath === undefined ?
                             '' : PDFJS.imageResourcesPath);
 
-/**
- * Disable the web worker and run all code on the main thread. This will
- * happen automatically if the browser doesn't support workers or sending
- * typed arrays to workers.
- * @var {boolean}
- */
-PDFJS.disableWorker = (PDFJS.disableWorker === undefined ?
-                       false : PDFJS.disableWorker);
-
 /**
  * Path and filename of the worker file. Required when the worker is enabled
  * in development mode. If unspecified in the production build, the worker
@@ -148,8 +139,7 @@ PDFJS.disableWorker = (PDFJS.disableWorker === undefined ?
 PDFJS.workerSrc = (PDFJS.workerSrc === undefined ? null : PDFJS.workerSrc);
 
 /**
- * Defines global port for worker process. Overrides workerSrc and
- * disableWorker setting.
+ * Defines global port for worker process. Overrides `workerSrc` setting.
  */
 PDFJS.workerPort = (PDFJS.workerPort === undefined ? null : PDFJS.workerPort);
 
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index 955200effd477..12252e07957ff 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -122,16 +122,14 @@ describe('api', function() {
             path: TEST_PDFS_PATH.node + basicApiFileName,
           });
         } else {
-          var nonBinaryRequest = PDFJS.disableWorker;
-          var request = new XMLHttpRequest();
+          let nonBinaryRequest = false;
+          let request = new XMLHttpRequest();
           request.open('GET', TEST_PDFS_PATH.dom + basicApiFileName, false);
-          if (!nonBinaryRequest) {
-            try {
-              request.responseType = 'arraybuffer';
-              nonBinaryRequest = request.responseType !== 'arraybuffer';
-            } catch (e) {
-              nonBinaryRequest = true;
-            }
+          try {
+            request.responseType = 'arraybuffer';
+            nonBinaryRequest = request.responseType !== 'arraybuffer';
+          } catch (e) {
+            nonBinaryRequest = true;
           }
           if (nonBinaryRequest && request.overrideMimeType) {
             request.overrideMimeType('text/plain; charset=x-user-defined');
diff --git a/web/app.js b/web/app.js
index edeea6ec3969b..3bfa7e893daa1 100644
--- a/web/app.js
+++ b/web/app.js
@@ -22,8 +22,8 @@ import {
 } from './ui_utils';
 import {
   build, createBlob, getDocument, getFilenameFromUrl, InvalidPDFException,
-  MissingPDFException, OPS, PDFJS, shadow, UnexpectedResponseException,
-  UNSUPPORTED_FEATURES, version
+  MissingPDFException, OPS, PDFJS, PDFWorker, shadow,
+  UnexpectedResponseException, UNSUPPORTED_FEATURES, version
 } from 'pdfjs-lib';
 import { CursorTool, PDFCursorTools } from './pdf_cursor_tools';
 import { PDFRenderingQueue, RenderingStates } from './pdf_rendering_queue';
@@ -285,8 +285,9 @@ let PDFViewerApplication = {
       let hash = document.location.hash.substring(1);
       let hashParams = parseQueryString(hash);
 
-      if ('disableworker' in hashParams) {
-        PDFJS.disableWorker = (hashParams['disableworker'] === 'true');
+      if ('disableworker' in hashParams &&
+          hashParams['disableworker'] === 'true') {
+        waitOn.push(loadFakeWorker());
       }
       if ('disablerange' in hashParams) {
         PDFJS.disableRange = (hashParams['disablerange'] === 'true');
@@ -1512,6 +1513,35 @@ if (typeof PDFJSDev === 'undefined' || PDFJSDev.test('GENERIC')) {
   };
 }
 
+function loadFakeWorker() {
+  return new Promise(function(resolve, reject) {
+    if (typeof PDFJSDev === 'undefined' || !PDFJSDev.test('PRODUCTION')) {
+      if (typeof SystemJS === 'object') {
+        SystemJS.import('pdfjs/core/worker').then((worker) => {
+          window.pdfjsNonProductionPdfWorker = worker;
+          resolve();
+        });
+      } else if (typeof require === 'function') {
+        window.pdfjsNonProductionPdfWorker = require('../src/core/worker.js');
+        resolve();
+      } else {
+        reject(new Error(
+          'SystemJS or CommonJS must be used to load fake worker.'));
+      }
+    } else {
+      let script = document.createElement('script');
+      script.src = PDFWorker.getWorkerSrc();
+      script.onload = function() {
+        resolve();
+      };
+      script.onerror = function() {
+        reject(new Error(`Cannot load fake worker at: ${script.src}`));
+      };
+      (document.head || document.documentElement).appendChild(script);
+    }
+  });
+}
+
 function loadAndEnablePDFBug(enabledTabs) {
   return new Promise(function (resolve, reject) {
     let appConfig = PDFViewerApplication.appConfig;

From 39c5e1ed1a7e7c24d0df6f373e8d72ce8d4c5156 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Sat, 20 Jan 2018 17:15:16 +0100
Subject: [PATCH 4/4] Remove the (unnecessary) `WorkerMessageHandler` variable
 from the `setupFakeWorkerGlobal()` function in the `src/display/api.js` file

---
 src/display/api.js | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/display/api.js b/src/display/api.js
index c62c3e7c1bca2..2a913d3adecb8 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -1233,7 +1233,6 @@ var PDFWorker = (function PDFWorkerClosure() {
 
   // Loads worker code into main thread.
   function setupFakeWorkerGlobal() {
-    var WorkerMessageHandler;
     if (fakeWorkerFilesLoadedCapability) {
       return fakeWorkerFilesLoadedCapability.promise;
     }
@@ -1245,26 +1244,24 @@ var PDFWorker = (function PDFWorkerClosure() {
       fakeWorkerFilesLoadedCapability.resolve(mainWorkerMessageHandler);
       return fakeWorkerFilesLoadedCapability.promise;
     }
-    // In the developer build load worker_loader which in turn loads all the
+    // In the developer build load worker_loader.js which in turn loads all the
     // other files and resolves the promise. In production only the
     // pdf.worker.js file is needed.
     if (typeof PDFJSDev === 'undefined' || !PDFJSDev.test('PRODUCTION')) {
       if (typeof SystemJS === 'object') {
         SystemJS.import('pdfjs/core/worker').then((worker) => {
-          WorkerMessageHandler = worker.WorkerMessageHandler;
-          fakeWorkerFilesLoadedCapability.resolve(WorkerMessageHandler);
+          fakeWorkerFilesLoadedCapability.resolve(worker.WorkerMessageHandler);
         });
       } else if (typeof require === 'function') {
-        var worker = require('../core/worker.js');
-        WorkerMessageHandler = worker.WorkerMessageHandler;
-        fakeWorkerFilesLoadedCapability.resolve(WorkerMessageHandler);
+        let worker = require('../core/worker.js');
+        fakeWorkerFilesLoadedCapability.resolve(worker.WorkerMessageHandler);
       } else {
         throw new Error(
           'SystemJS or CommonJS must be used to load fake worker.');
       }
     } else {
-      var loader = fakeWorkerFilesLoader || function (callback) {
-        Util.loadScript(getWorkerSrc(), function () {
+      let loader = fakeWorkerFilesLoader || function(callback) {
+        Util.loadScript(getWorkerSrc(), function() {
           callback(window.pdfjsDistBuildPdfWorker.WorkerMessageHandler);
         });
       };