Issue 5161 - Use maps and sets where appropriate

lib/popupBlocker.js

Index: lib/popupBlocker.js
===================================================================
--- a/lib/popupBlocker.js
+++ b/lib/popupBlocker.js
@@ -20,28 +20,23 @@
 "use strict";
 
 const {defaultMatcher} = require("matcher");
 const {BlockingFilter, RegExpFilter} = require("filterClasses");
 const {stringifyURL, isThirdParty, extractHostFromFrame} = require("url");
 const {checkWhitelisted} = require("whitelisting");
 const {logRequest} = require("devtools");
 
-let loadingPopups = Object.create(null);
-
-function hasLoadingPopups()
-{
-  return Object.keys(loadingPopups).length > 0;
-}
+let loadingPopups = new Map();
 
 function forgetPopup(tabId)
 {
-  delete loadingPopups[tabId];
+  loadingPopups.delete(tabId);
 
-  if (!hasLoadingPopups())
+  if (loadingPopups.size == 0)
   {
     chrome.webRequest.onBeforeRequest.removeListener(onPopupURLChanged);
     chrome.webNavigation.onCommitted.removeListener(onPopupURLChanged);
     chrome.webNavigation.onCompleted.removeListener(onCompleted);
     chrome.tabs.onRemoved.removeListener(forgetPopup);
   }
 }
 
@@ -73,53 +68,57 @@
 }
 
 function onPopupURLChanged(details)
 {
   // Ignore frames inside the popup window.
   if (details.frameId != 0)
     return;
 
-  let popup = loadingPopups[details.tabId];
+  let popup = loadingPopups.get(details.tabId);
   if (popup)
   {
     popup.url = details.url;
     if (popup.sourceFrame)
       checkPotentialPopup(details.tabId, popup);
   }
 }
 
 function onCompleted(details)
 {
   if (details.frameId == 0 && details.url != "about:blank")
     forgetPopup(details.tabId);
 }
 
 chrome.webNavigation.onCreatedNavigationTarget.addListener(details =>
 {
-  if (!hasLoadingPopups())
+  if (loadingPopups.size == 0)
   {
     chrome.webRequest.onBeforeRequest.addListener(
       onPopupURLChanged,
       {
         urls: ["<all_urls>"],
         types: ["main_frame"]
       }
     );
     chrome.webNavigation.onCommitted.addListener(onPopupURLChanged);
     chrome.webNavigation.onCompleted.addListener(onCompleted);
     chrome.tabs.onRemoved.addListener(forgetPopup);
   }
 
   let {tabId} = details;
-  let popup = loadingPopups[tabId] = {
+
+  let popup = {
     url: details.url,
     sourcePage: new ext.Page({id: details.sourceTabId}),
     sourceFrame: null
   };
+
+  loadingPopups.set(tabId, popup);
+
   let frame = ext.getFrame(details.sourceTabId, details.sourceFrameId);
 
   if (checkWhitelisted(popup.sourcePage, frame))
   {
     forgetPopup(tabId);
   }
   else
   {