Fix rendering of fonts on Firefox + turn worker on again.

Seems like Gecko requires the fontName to start with a character, not a number.

pdf.js

@@ -3423,7 +3423,7 @@ var Page = (function() {
       
       var pe = this.pe = new PartialEvaluator();
       var IRQueue = {};
-      return this.IRQueue = pe.getIRQueue(content, xref, resources, IRQueue, fonts, images, this.pageNumber + "_");
+      return this.IRQueue = pe.getIRQueue(content, xref, resources, IRQueue, fonts, images, "p" + this.pageNumber + "_");
     },
     
     ensureFonts: function(fonts, callback) {

worker.js

@@ -111,7 +111,7 @@ var WorkerPDFDoc = (function() {
     
     this.pageCache = [];
     
-    var useWorker = false;
+    var useWorker = true;
     
     if (useWorker) {
       var worker = new Worker("../worker/boot.js");