Issue 4795 - Use modern JavaScript syntax

composer.postload.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 165 matching lines @@
 
     highlightElement(overlay, shadowColor, backgroundColor);
     overlay.style.pointerEvents = "none";
 
     element._unhighlight = () =>
     {
       overlay.parentNode.removeChild(overlay);
     };
   };
 
-  let highlightWithStyleAttribute = () => 
+  let highlightWithStyleAttribute = () =>
   {
     let originalBoxShadow = element.style.getPropertyValue("box-shadow");
     let originalBoxShadowPriority =
       element.style.getPropertyPriority("box-shadow");
     let originalBackgroundColor =
       element.style.getPropertyValue("background-color");
     let originalBackgroundColorPriority =
       element.style.getPropertyPriority("background-color");
 
     element.style.setProperty("box-shadow", "inset 0px 0px 5px " + shadowColor,
@@ skipping 384 matching lines @@
             }
           });
         }
         break;
     }
   });
 
   if (window == window.top)
     ext.backgroundPage.sendMessage({type: "composer.ready"});
 }