ported from custom branch of UXP: [Basilisk] port PM's ghostbuster (d1fde5c4)

application/basilisk/app/profile/firefox.js

@@ -477,6 +477,9 @@ pref("javascript.options.showInConsole",          true);
 pref("general.warnOnAboutConfig",                 false);
 #endif
 
+// Enable unlinking of ghost windows so they can be garbage collected.
+pref("browser.ghostbuster.enabled",               true);
+
 // This is the pref to control the location bar, change this to true to
 // force this - this makes the origin of popup windows more obvious to avoid
 // spoofing. We would rather not do it by default because it affects UE for web

application/basilisk/base/content/tabbrowser.xml

@@ -2736,12 +2736,24 @@
             }
 
             // We're going to remove the tab and the browser now.
+
+            // Using the "STOP_ALL" flag should halt all animations, fetches, network
+            // activity, etc. to come to a clean state for removal and unlinking (if enabled).
+            var browser = this.getBrowserForTab(aTab);
+            browser.webNavigation.stop(nsIWebNavigation.STOP_ALL);
+
             this._tabFilters.delete(aTab);
             this._tabListeners.delete(aTab);
 
-            var browser = this.getBrowserForTab(aTab);
             this._outerWindowIDBrowserMap.delete(browser.outerWindowID);
 
+            if (Services.prefs.getBoolPref("browser.ghostbuster.enabled", true)) {
+              Cu.unlinkGhostWindows();
+#ifdef DEBUG
+              dump("Unlinking ghost windows has run on tab close.\n");
+#endif
+            }
+
             // Because of the way XBL works (fields just set JS
             // properties on the element) and the code we have in place
             // to preserve the JS objects for any elements that have

application/basilisk/components/nsBrowserGlue.js

@@ -107,6 +107,10 @@ const BOOKMARKS_BACKUP_MIN_INTERVAL_DAYS = 1;
 // days we will try to create a new one more aggressively.
 const BOOKMARKS_BACKUP_MAX_INTERVAL_DAYS = 3;
 
+// Use users' idle time to unlink ghost windows and clean up memory.
+// Trigger this by default every 5 minutes.
+const GHOSTBUSTER_INTERVAL = 5 * 60;
+
 // Factory object
 const BrowserGlueServiceFactory = {
   _instance: null,
@@ -125,6 +129,10 @@ function BrowserGlue() {
                                      "@mozilla.org/widget/idleservice;1",
                                      "nsIIdleService");
 
+  XPCOMUtils.defineLazyServiceGetter(this, "_ghostBusterService",
+                                     "@mozilla.org/widget/idleservice;1",
+                                     "nsIIdleService");
+
   XPCOMUtils.defineLazyGetter(this, "_distributionCustomizer", function() {
                                 Cu.import("resource:///modules/distribution.js");
                                 return new DistributionCustomizer();
@@ -157,6 +165,7 @@ BrowserGlue.prototype = {
   _isPlacesShutdownObserver: false,
   _isPlacesDatabaseLocked: false,
   _migrationImportsDefaultBookmarks: false,
+  _isGhostBusterObserver: false,
 
   _setPrefToSaveSession: function BG__setPrefToSaveSession(aForce) {
     if (!this._saveSession && !aForce)
@@ -276,6 +285,15 @@ BrowserGlue.prototype = {
         break;
       case "idle":
         this._backupBookmarks();
+        if (this._ghostBusterService.idleTime > GHOSTBUSTER_INTERVAL * 1000) {
+          if (Services.prefs.getBoolPref("browser.ghostbuster.enabled", true)) {
+            Cu.unlinkGhostWindows();
+            Cu.forceGC();
+#ifdef DEBUG
+            dump("Unlinking ghost windows + GC has run on idle.\n");
+#endif
+          }
+        }
         break;
       case "distribution-customization-complete":
         Services.obs.removeObserver(this, "distribution-customization-complete");
@@ -919,6 +937,13 @@ BrowserGlue.prototype = {
 
     this._trackSlowStartup();
 
+    // Initialize ghost window idle observer.
+    if (!this._isGhostBusterObserver) {
+      this._ghostBusterService.addIdleObserver(this, GHOSTBUSTER_INTERVAL);
+      // Prevent re-entry.
+      this._isGhostBusterObserver = true;
+    }
+
     // Offer to reset a user's profile if it hasn't been used for 60 days.
     const OFFER_PROFILE_RESET_INTERVAL_MS = 60 * 24 * 60 * 60 * 1000;
     let lastUse = Services.appinfo.replacedLockTime;
@@ -998,6 +1023,13 @@ BrowserGlue.prototype = {
 #ifdef NIGHTLY_BUILD
     AddonWatcher.uninit();
 #endif
+    // Shut down ghost window idle observer.
+    if (this._isGhostBusterObserver) {
+      this._ghostBusterService.removeIdleObserver(this, GHOSTBUSTER_INTERVAL);
+      this._isGhostBusterObserver = false;
+    }
+    // Do one final unlink to combat shutdown issues.
+    Cu.unlinkGhostWindows();
   },
 
   _initServiceDiscovery() {