Issue 5161 - Use maps and sets where appropriate

lib/whitelisting.js

Index: lib/whitelisting.js
===================================================================
--- a/lib/whitelisting.js
+++ b/lib/whitelisting.js
@@ -123,17 +123,17 @@
 exports.getKey = (page, frame) =>
 {
   let keys = sitekeys.get(page);
   if (!keys)
     return null;
 
   for (; frame != null; frame = frame.parent)
   {
-    let key = keys[stringifyURL(frame.url)];
+    let key = keys.get(stringifyURL(frame.url));
     if (key)
       return key;
   }
 
   return null;
 };
 
 function checkKey(token, url)
@@ -153,20 +153,20 @@
   return key;
 }
 
 function recordKey(key, page, url)
 {
   let keys = sitekeys.get(page);
   if (!keys)
   {
-    keys = Object.create(null);
+    keys = new Map();
     sitekeys.set(page, keys);
   }
-  keys[stringifyURL(url)] = key;
+  keys.set(stringifyURL(url), key);
 }
 
 port.on("filters.addKey", (message, sender) =>
 {
   let key = checkKey(message.token, sender.frame.url);
   if (key)
     recordKey(key, sender.page, sender.frame.url);
 });