Bug 545228 - Firefox leaks the world on Windows 7. r=robarnold

browser/components/wintaskbar/WindowsPreviewPerTab.jsm

@@ -180,6 +180,12 @@ PreviewController.prototype = {
     this.linkedBrowser.removeEventListener("pageshow", this, false);
     this.linkedBrowser.removeEventListener("DOMTitleChanged", this, false);
     this.linkedBrowser.removeEventListener("MozAfterPaint", this, false);
+
+    // Break cycles, otherwise we end up leaking the window with everything
+    // attached to it.
+    delete this.win;
+    delete this.preview;
+    delete this.dirtyRegion;
   },
   get wrappedJSObject() {
     return this;
@@ -383,7 +389,6 @@ function TabWindow(win) {
     this.tabbrowser.tabContainer.addEventListener(this.events[i], this, false);
   this.tabbrowser.addTabsProgressListener(this);
 
-
   AeroPeek.windows.push(this);
   let tabs = this.tabbrowser.tabs;
   for (let i = 0; i < tabs.length; i++)
@@ -402,6 +407,8 @@ TabWindow.prototype = {
 
     let tabs = this.tabbrowser.tabs;
 
+    this.tabbrowser.removeTabsProgressListener(this);
+
     for (let i = 0; i < this.events.length; i++)
       this.tabbrowser.tabContainer.removeEventListener(this.events[i], this, false);
 
@@ -589,6 +596,17 @@ var AeroPeek = {
     this.enabled = this._prefenabled = this.prefs.getBoolPref(TOGGLE_PREF_NAME);
   },
 
+  destroy: function destroy() {
+    this._enabled = false;
+
+    this.prefs.removeObserver(TOGGLE_PREF_NAME, this);
+    this.prefs.removeObserver(DISABLE_THRESHOLD_PREF_NAME, this);
+    this.prefs.removeObserver(CACHE_EXPIRATION_TIME_PREF_NAME, this);
+
+    if (this.cacheTimer)
+      this.cacheTimer.cancel();
+  },
+
   get enabled() {
     return this._enabled;
   },
@@ -636,7 +654,10 @@ var AeroPeek = {
       return;
 
     win.gTaskbarTabGroup.destroy();
-    win.gTaskbarTabGroup = null;
+    delete win.gTaskbarTabGroup;
+
+    if (this.windows.length == 0)
+      this.destroy();
   },
 
   resetCacheTimer: function () {