[api-minor] Remove support for browsers/environments without fully working URL.createObjectURL implementations

This `disableCreateObjectURL` option was originally introduced all the way back in PR 4103 (eight years ago), in order to work-around `URL.createObjectURL()`-bugs specific to Internet Explorer.
In PR 8081 (five years ago) the `disableCreateObjectURL` option was extended to cover Google Chrome on iOS-devices as well, since that configuration apparently also suffered from `URL.createObjectURL()`-bugs.[1]

At this point in time, I thus think that it makes sense to re-evaluate if we should still keep the `disableCreateObjectURL` option.

 - For Internet Explorer, support was explicitly removed in PDF.js version `2.7.570` which was released one year ago and all IE-specific compatibility code (and polyfills) have since been removed.

 - For Google Chrome on iOS-devices, while we still "support" such configurations, it's *not* the focus of any development and platform-specific bugs are thus often closed as WONTFIX.

Note here that at this point in time, the `disableCreateObjectURL` option is *only* being used in the viewer and browser/platform bugs will thus not affect the main PDF.js library. Furthermore, given where the `disableCreateObjectURL` option is being used in the viewer the basic functionality should also remain unaffected by these changes.[2]
Furthermore, it's also possible that the `URL.createObjectURL()`-bugs have been fixed in *browser* itself since PR 8081 was submitted.[3]

Obviously you could argue that this isn't a lot of code, w.r.t. number of lines, and you'd be technically correct. However, it does add additional complexity in a few different viewer components which thus add overhead when reading and working with this code.
Finally, assuming the `URL.createObjectURL()`-bugs are still present in Google Chrome on iOS-devices, I think that we should ask ourselves if it's reasonable for the PDF.js project (and its contributors) to keep attempting to support a configuration if the *browser* developers still haven't fixed these kind of bugs!?

---
[1] According to https://groups.google.com/a/chromium.org/forum/#!topic/chromium-html5/RKQ0ZJIj7c4, which is linked in PR 8081, that bug was mentioned/reported as early as the 2014 (eight years ago).

[2] Viewer functionality such as e.g. downloading and printing may be affected.

[3] I don't have access to any iOS-devices to test with.

Author: Snuffleupagus

web/app.js

@@ -35,7 +35,7 @@ import {
   SpreadMode,
   TextLayerMode,
 } from "./ui_utils.js";
-import { AppOptions, compatibilityParams, OptionKind } from "./app_options.js";
+import { AppOptions, OptionKind } from "./app_options.js";
 import { AutomationEventBus, EventBus } from "./event_utils.js";
 import {
   build,
@@ -2490,22 +2490,11 @@ if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
     }
     const file = evt.fileInput.files[0];
 
-    if (!compatibilityParams.disableCreateObjectURL) {
-      let url = URL.createObjectURL(file);
-      if (file.name) {
-        url = { url, originalUrl: file.name };
-      }
-      PDFViewerApplication.open(url);
-    } else {
-      PDFViewerApplication.setTitleUsingUrl(file.name);
-      // Read the local file into a Uint8Array.
-      const fileReader = new FileReader();
-      fileReader.onload = function webViewerChangeFileReaderOnload(event) {
-        const buffer = event.target.result;
-        PDFViewerApplication.open(new Uint8Array(buffer));
-      };
-      fileReader.readAsArrayBuffer(file);
+    let url = URL.createObjectURL(file);
+    if (file.name) {
+      url = { url, originalUrl: file.name };
     }
+    PDFViewerApplication.open(url);
   };
 
   webViewerOpenFile = function (evt) {

web/app_options.js

@@ -26,17 +26,6 @@ if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
   const isIOS =
     /\b(iPad|iPhone|iPod)(?=;)/.test(userAgent) ||
     (platform === "MacIntel" && maxTouchPoints > 1);
-  const isIOSChrome = /CriOS/.test(userAgent);
-
-  // Disables URL.createObjectURL() usage in some environments.
-  // Support: Chrome on iOS
-  (function checkOnBlobSupport() {
-    // Sometimes Chrome on iOS loses data created with createObjectURL(),
-    // see issue 8081.
-    if (isIOSChrome) {
-      compatibilityParams.disableCreateObjectURL = true;
-    }
-  })();
 
   // Limit canvas size to 5 mega-pixels on mobile.
   // Support: Android, iOS

web/download_manager.js

@@ -15,8 +15,7 @@
 
 /** @typedef {import("./interfaces").IDownloadManager} IDownloadManager */
 
-import { createObjectURL, createValidAbsoluteUrl, isPdfFile } from "pdfjs-lib";
-import { compatibilityParams } from "./app_options.js";
+import { createValidAbsoluteUrl, isPdfFile } from "pdfjs-lib";
 
 if (typeof PDFJSDev !== "undefined" && !PDFJSDev.test("CHROME || GENERIC")) {
   throw new Error(
@@ -61,10 +60,8 @@ class DownloadManager {
   }
 
   downloadData(data, filename, contentType) {
-    const blobUrl = createObjectURL(
-      data,
-      contentType,
-      compatibilityParams.disableCreateObjectURL
+    const blobUrl = URL.createObjectURL(
+      new Blob([data], { type: contentType })
     );
     download(blobUrl, filename);
   }
@@ -76,7 +73,7 @@ class DownloadManager {
     const isPdfData = isPdfFile(filename);
     const contentType = isPdfData ? "application/pdf" : "";
 
-    if (isPdfData && !compatibilityParams.disableCreateObjectURL) {
+    if (isPdfData) {
       let blobUrl = this._openBlobUrls.get(element);
       if (!blobUrl) {
         blobUrl = URL.createObjectURL(new Blob([data], { type: contentType }));
@@ -119,11 +116,6 @@ class DownloadManager {
    *   the "open with" dialog.
    */
   download(blob, url, filename, sourceEventType = "download") {
-    if (compatibilityParams.disableCreateObjectURL) {
-      // URL.createObjectURL is not supported
-      this.downloadUrl(url, filename);
-      return;
-    }
     const blobUrl = URL.createObjectURL(blob);
     download(blobUrl, filename);
   }

web/pdf_page_view.js

@@ -913,11 +913,7 @@ class PDFPageView {
       })
       .then(opList => {
         ensureNotCancelled();
-        const svgGfx = new SVGGraphics(
-          pdfPage.commonObjs,
-          pdfPage.objs,
-          /* forceDataSchema = */ compatibilityParams.disableCreateObjectURL
-        );
+        const svgGfx = new SVGGraphics(pdfPage.commonObjs, pdfPage.objs);
         return svgGfx.getSVG(opList, actualSizeViewport).then(svg => {
           ensureNotCancelled();
           this.svg = svg;

web/pdf_print_service.js

@@ -15,7 +15,6 @@
 
 import { AnnotationMode, PixelsPerInch } from "pdfjs-lib";
 import { PDFPrintServiceFactory, PDFViewerApplication } from "./app.js";
-import { compatibilityParams } from "./app_options.js";
 import { getXfaHtmlForPrinting } from "./print_utils.js";
 
 let activeService = null;
@@ -176,10 +175,7 @@ PDFPrintService.prototype = {
     this.throwIfInactive();
     const img = document.createElement("img");
     const scratchCanvas = this.scratchCanvas;
-    if (
-      "toBlob" in scratchCanvas &&
-      !compatibilityParams.disableCreateObjectURL
-    ) {
+    if ("toBlob" in scratchCanvas) {
       scratchCanvas.toBlob(function (blob) {
         img.src = URL.createObjectURL(blob);
       });