Add an Array.from polyfill, using core-js, and remove some compatibility hacks from the src/display/content_disposition.js file

src/display/content_disposition.js

@@ -18,8 +18,6 @@
 // with the following changes:
 // - Modified to conform to PDF.js's coding style.
 // - Support UTF-8 decoding when TextDecoder is unsupported.
-// - Replace Array.from with Array + loop for compat with old browsers.
-// - Replace "startsWith" with other string method for compat with old browsers.
 // - Move return to the end of the function to prevent Babel from dropping the
 //   function declarations.
 
@@ -83,10 +81,9 @@ function getFilenameFromContentDispositionHeader(contentDisposition) {
       }
       try {
         let decoder = new TextDecoder(encoding, { fatal: true, });
-        let bytes = new Array(value.length);
-        for (let i = 0; i < value.length; ++i) {
-          bytes[i] = value.charCodeAt(i);
-        }
+        let bytes = Array.from(value, function(ch) {
+          return ch.charCodeAt(0) & 0xFF;
+        });
         value = decoder.decode(new Uint8Array(bytes));
         needsEncodingFixup = false;
       } catch (e) {
@@ -151,7 +148,7 @@ function getFilenameFromContentDispositionHeader(contentDisposition) {
     return parts.join('');
   }
   function rfc2616unquote(value) {
-    if (value.charAt(0) === '"') {
+    if (value.startsWith('"')) {
       let parts = value.slice(1).split('\\"');
       // Find the first unescaped " and terminate there.
       for (let i = 0; i < parts.length; ++i) {
@@ -192,7 +189,7 @@ function getFilenameFromContentDispositionHeader(contentDisposition) {
 
     // Firefox also decodes words even where RFC 2047 section 5 states:
     // "An 'encoded-word' MUST NOT appear within a 'quoted-string'."
-    if (value.slice(0, 2) !== '=?' || /[\x00-\x19\x80-\xff]/.test(value)) {
+    if (!value.startsWith('=?') || /[\x00-\x19\x80-\xff]/.test(value)) {
       return value;
     }
     // RFC 2047, section 2.4

src/shared/compatibility.js

@@ -151,6 +151,15 @@ const hasDOM = typeof window === 'object' && typeof document === 'object';
   require('core-js/fn/array/includes');
 })();
 
+// Provides support for Array.from in legacy browsers.
+// Support: IE
+(function checkArrayFrom() {
+  if (Array.from) {
+    return;
+  }
+  require('core-js/fn/array/from');
+})();
+
 // Provides support for Object.assign in legacy browsers.
 // Support: IE
 (function checkObjectAssign() {