Disable PDFJS worker (#3910)

webapp/root.jsx

@@ -7,6 +7,7 @@ require('perfect-scrollbar/jquery')($);
 import React from 'react';
 import ReactDOM from 'react-dom';
 import {Router, browserHistory} from 'react-router/es6';
+import PDFJS from 'pdfjs-dist';
 import * as GlobalActions from 'actions/global_actions.jsx';
 import * as Websockets from 'actions/websocket_actions.jsx';
 import BrowserStore from 'stores/browser_store.jsx';
@@ -21,6 +22,8 @@ import 'katex/dist/katex.min.css';
 // Import the root of our routing tree
 import rRoot from 'routes/route_root.jsx';
 
+PDFJS.disableWorker = true;
+
 // This is for anything that needs to be done for ALL react components.
 // This runs before we start to render anything.
 function preRenderSetup(callwhendone) {