Fix leaks caused by cyclical ownership and XPCOM timers. b=315951 r=mconnor

embedding/components/ui/helperAppDlg/nsHelperAppDlg.js

@@ -381,8 +381,10 @@ nsHelperAppDialog.prototype = {
 
     _timer: null,
     notify: function (aTimer) {
-        if (!this._blurred)
-          this.mDialog.document.documentElement.getButton('accept').disabled = false;
+        try { // The user may have already canceled the dialog.
+          if (!this._blurred)
+            this.mDialog.document.documentElement.getButton('accept').disabled = false;
+        } catch (ex) {}
         this._timer = null;
     },
 

toolkit/content/widgets/preferences.xml

@@ -606,6 +606,20 @@
       ]]>
       </constructor>
 
+      <destructor>
+      <![CDATA[
+        // Release timers to avoid reference cycles.
+        if (this._animateTimer) {
+          this._animateTimer.cancel();
+          this._animateTimer = null;
+        }
+        if (this._fadeTimer) {
+          this._fadeTimer.cancel();
+          this._fadeTimer = null;
+        }
+      ]]>
+      </destructor>
+
       <field name="instantApply">false</field>
       
       <property name="preferencePanes"
@@ -806,10 +820,10 @@
               this._setUpFadeTimer();
             }
           } else if (aTimer == this._fadeTimer) {
-            var lastSelectedPane = document.getElementById(this.lastSelected);
             var elt = document.getElementById(this.lastSelected);
-            if (parseFloat(window.getComputedStyle(lastSelectedPane, "").opacity) < (1.0 - this._fadeIncrement))
-              elt.style.opacity = parseFloat(window.getComputedStyle(elt, "").opacity) + this._fadeIncrement;
+            var newOpacity = parseFloat(window.getComputedStyle(elt, "").opacity) + this._fadeIncrement;
+            if (newOpacity < 1.0)
+              elt.style.opacity = newOpacity;
             else {
               aTimer.cancel();
               elt.style.opacity = 1.0;

toolkit/mozapps/downloads/src/nsHelperAppDlg.js.in

@@ -450,9 +450,12 @@ nsUnknownContentTypeDialog.prototype = {
     
     _timer: null,
     notify: function (aTimer) {
-      if (!this._blurred)
-        this.mDialog.document.documentElement.getButton('accept').disabled = false;
+      try { // The user may have already canceled the dialog.
+        if (!this._blurred)
+          this.mDialog.document.documentElement.getButton('accept').disabled = false;
+      } catch (ex) {}
       this._delayExpired = true;
+      this._timer = null; // the timer won't release us, so we have to release it
     },
     
     postShowCallback: function () {