De-inline CSS for the 'open file' button

web/viewer.css

@@ -1434,6 +1434,10 @@ canvas {
   background: white;
   color: black;
   margin-top: 5px;
+  visibility: hidden;
+  position: fixed;
+  right: 0;
+  top: 0;
 }
 
 #PDFBug {

web/viewer.js

@@ -1572,8 +1572,6 @@ document.addEventListener('DOMContentLoaded', function webViewerLoad(evt) {
   fileInput.id = 'fileInput';
   fileInput.className = 'fileInput';
   fileInput.setAttribute('type', 'file');
-  fileInput.setAttribute('style',
-    'visibility: hidden; position: fixed; right: 0; top: 0');
   fileInput.oncontextmenu = noContextMenuHandler;
   document.body.appendChild(fileInput);