Fixed: Glass pane doesn`t properly cover up the first-run page if the page is scrolled

skin/firstRun.css

 body
 {
   font-family: Arial, Helvetica, sans-serif;
   font-size: 20px;
   background: repeating-linear-gradient(0deg, #F8F6F5, #F6F4F2 50%, #FCFBF9);
   background: -webkit-repeating-linear-gradient(0deg, #F5F4F3, #FAF9F8 50%, #F5F4F3);
   background-size: 5px 5px;
   max-width: 800px;
   margin: auto;
   line-height: 1.5;
@@ skipping 106 matching lines @@
 #glass-pane, #share-popup
 {
   visibility: hidden;
   opacity: 0;
   -webkit-transition-property: opacity, visibility;
   transition-property: opacity, visibility;
 }
 
 #glass-pane
 {
-  position: absolute;
+  position: fixed;
   top: 0;
   right: 0;
   bottom: 0;
   left: 0;
   background: rgba(0, 0, 0, 0.5) url(/skin/ajax-loader.gif) no-repeat 50% 50%;
 
   display: -webkit-box;
   -webkit-box-orient: horizontal;
   -webkit-box-pack: center;
   -webkit-box-align: center;
@@ skipping 43 matching lines @@
   }
 }
 
 @media (max-height: 700px)
 {
   body
   {
     font-size: 16px;
   }
 }