Issue 2259 - Removed non-standard JavaScript code from Element Hiding Helper

chrome/content/composer.js

Index: chrome/content/composer.js
===================================================================
--- a/chrome/content/composer.js
+++ b/chrome/content/composer.js
@@ -101,11 +101,10 @@
     };
   }
   else {
-    obj.__defineGetter__(key, function() {
-      return orig[key];
-    });
-    obj.__defineSetter__(key, function(value) {
-      orig[key] = value;
+    Object.defineProperty(obj, key, {
+      get: () => orig[key],
+      set: value => { orig[key] = value; },
+      enumerable: true
     });
   }
 }
@@ -250,11 +249,11 @@
           else if (attr.name == "class" && /\S/.test(attr.selected))
           {
             let knownClasses = {};
-            for each (let cls in attr.value.split(/\s+/))
+            for (let cls of attr.value.split(/\s+/))
               knownClasses[cls] = true;
 
-            let classes = attr.selected.split(/\s+/).filter(function(cls) cls != "");
-            if (classes.every(function(cls) knownClasses.hasOwnProperty(cls)))
+            let classes = attr.selected.split(/\s+/).filter(cls => cls != "");
+            if (classes.every(cls => knownClasses.hasOwnProperty(cls)))
               expression += "." + classes.map(escapeName).join(".");
             else
               useFallback = true;