apply pdfjs font patch

https://github.com/mozilla/pdf.js/issues/2594#issuecomment-247644205

services/web/public/js/libs/pdfjs-1.3.91p1/pdf.worker.js

@@ -18017,7 +18017,7 @@ var Font = (function FontClosure() {
   }
 
   /**
-   * Helper function for |adjustMapping|.
+   * Helper function for `adjustMapping`.
    * @return {boolean}
    */
   function isProblematicUnicodeLocation(code) {
@@ -18060,12 +18060,18 @@ var Font = (function FontClosure() {
       var fontCharCode = originalCharCode;
       // First try to map the value to a unicode position if a non identity map
       // was created.
+      var hasUnicodeValue = false;
       if (!isIdentityUnicode && toUnicode.has(originalCharCode)) {
         var unicode = toUnicode.get(fontCharCode);
         // TODO: Try to map ligatures to the correct spot.
         if (unicode.length === 1) {
           fontCharCode = unicode.charCodeAt(0);
         }
+        // For Symbolic fonts, we trust the `unicode` value if and only if the
+        // font includes either `ToUnicode` or `Encoding` data, since otherwise
+        // `toUnicode` may not be correct.
+        hasUnicodeValue = properties.hasIncludedToUnicodeMap ||
+                          properties.hasEncoding;
       }
       // Try to move control characters, special characters and already mapped
       // characters to the private use area since they will not be drawn by
@@ -18075,7 +18081,7 @@ var Font = (function FontClosure() {
       // with firefox and thuluthfont).
       if ((usedFontCharCodes[fontCharCode] !== undefined ||
            isProblematicUnicodeLocation(fontCharCode) ||
-           (isSymbolic && isIdentityUnicode)) &&
+           (isSymbolic && !hasUnicodeValue)) &&
           nextAvailableFontCharCode <= PRIVATE_USE_OFFSET_END) { // Room left.
         // Loop to try and find a free spot in the private use area.
         do {