Issue 5161 - Use maps and sets where appropriate

lib/devtools.js

Index: lib/devtools.js
===================================================================
--- a/lib/devtools.js
+++ b/lib/devtools.js
@@ -27,26 +27,21 @@
 const {extractHostFromFrame} = require("url");
 const {port} = require("messaging");
 
 const nonRequestTypes = ["DOCUMENT", "ELEMHIDE", "GENERICBLOCK", "GENERICHIDE"];
 
 // Mapping of inspected tabs to their devpanel page
 // and recorded items. We can't use a PageMap here,
 // because data must persist after navigation/reload.
-let panels = Object.create(null);
-
-function hasPanels()
-{
-  return Object.keys(panels).length > 0;
-}
+let panels = new Map();
 
 function getActivePanel(page)
 {
-  let panel = panels[page.id];
+  let panel = panels.get(page.id);
   if (panel && !panel.reload && !panel.reloading)
     return panel;
   return null;
 }
 
 function getFilterInfo(filter)
 {
   if (!filter)
@@ -208,22 +203,22 @@
 /**
  * Checks whether a page is inspected by the devtools panel.
  *
  * @param {Page} page
  * @return {boolean}
  */
 exports.hasPanel = function(page)
 {
-  return page.id in panels;
+  return panels.has(page.id);
 };
 
 function onBeforeRequest(details)
 {
-  let panel = panels[details.tabId];
+  let panel = panels.get(details.tabId);
 
   // Clear the devtools panel and reload the inspected tab without caching
   // when a new request is issued. However, make sure that we don't end up
   // in an infinite recursion if we already triggered a reload.
   if (panel.reloading)
   {
     panel.reloading = false;
   }
@@ -238,37 +233,35 @@
     if (details.method == "GET")
       panel.reload = true;
   }
 }
 
 function onLoading(page)
 {
   let tabId = page.id;
-  let panel = panels[tabId];
+  let panel = panels.get(tabId);
 
   // Reloading the tab is the only way that allows bypassing all caches, in
   // order to see all requests in the devtools panel. Reloading must not be
   // performed before the tab changes to "loading", otherwise it will load the
   // previous URL.
   if (panel && panel.reload)
   {
     chrome.tabs.reload(tabId, {bypassCache: true});
 
     panel.reload = false;
     panel.reloading = true;
   }
 }
 
 function updateFilters(filters, added)
 {
-  for (let tabId in panels)
+  for (let panel of panels.values())
   {
-    let panel = panels[tabId];
-
     for (let i = 0; i < panel.records.length; i++)
     {
       let record = panel.records[i];
 
       // If an added filter matches a request shown in the devtools panel,
       // update that record to show the new filter. Ignore filters that aren't
       // associated with any sub-resource request. There is no record for these
       // if they don't already match. In particular, in case of element hiding
@@ -347,39 +340,39 @@
     localOnBeforeRequest,
     {
       urls: ["<all_urls>"],
       types: ["main_frame"],
       tabId: inspectedTabId
     }
   );
 
-  if (!hasPanels())
+  if (panels.size == 0)
   {
     ext.pages.onLoading.addListener(onLoading);
     FilterNotifier.on("filter.added", onFilterAdded);
     FilterNotifier.on("filter.removed", onFilterRemoved);
     FilterNotifier.on("subscription.added", onSubscriptionAdded);
   }
 
   newPort.onDisconnect.addListener(() =>
   {
-    delete panels[inspectedTabId];
+    panels.delete(inspectedTabId);
     chrome.webRequest.onBeforeRequest.removeListener(localOnBeforeRequest);
 
-    if (!hasPanels())
+    if (panels.size == 0)
     {
       ext.pages.onLoading.removeListener(onLoading);
       FilterNotifier.off("filter.added", onFilterAdded);
       FilterNotifier.off("filter.removed", onFilterRemoved);
       FilterNotifier.off("subscription.added", onSubscriptionAdded);
     }
   });
 
-  panels[inspectedTabId] = {port: newPort, records: []};
+  panels.set(inspectedTabId, {port: newPort, records: []});
 });
 
 port.on("devtools.traceElemHide", (message, sender) =>
 {
   logHiddenElements(
     sender.page, message.selectors, message.filters,
     extractHostFromFrame(sender.frame)
   );