Bug 341047 - After 'Close other tabs' tab's context menu contains scrollbars, r=mano

toolkit/content/widgets/scrollbox.xml

@@ -166,11 +166,17 @@
 
         this._scrollButtonUp.collapsed = true;
         this._scrollButtonDown.collapsed = true;
-        var childNodes = document.getAnonymousNodes(this._scrollbox);
-        if (childNodes && childNodes.length) {
-          this.ensureElementIsVisible(childNodes[0]);
-          if (childNodes.length > 1)
-            this.ensureElementIsVisible(childNodes[childNodes.length-1]);
+        try {
+          // See bug 341047 and comments in overflow handler as to why 
+          // try..catch is needed here
+          var childNodes = document.getAnonymousNodes(this._scrollbox);
+          if (childNodes && childNodes.length) {
+            if (childNodes.length > 0)
+              this.ensureElementIsVisible(childNodes[0]);
+        }
+        catch(e) {
+          this._scrollButtonUp.collapsed = false;
+          this._scrollButtonDown.collapsed = false;
         }
       ]]></handler>
 
@@ -181,7 +187,19 @@
 
         this._scrollButtonUp.collapsed = false;
         this._scrollButtonDown.collapsed = false;
-        this._updateScrollButtonsDisabledState();
+        try {
+          // See bug 341047, the overflow event is dispatched when the 
+          // scrollbox already is mostly destroyed. This causes some code in
+          // _updateScrollButtonsDisabledState() to throw an error. It also
+          // means that the scrollbarbuttons were uncollapsed when that should
+          // not be happening, because the whole overflow event should not be
+          // happening in that case.
+          this._updateScrollButtonsDisabledState();
+        } 
+        catch(e) {
+          this._scrollButtonUp.collapsed = true;
+          this._scrollButtonDown.collapsed = true;
+        }
       ]]></handler>
 
       <handler event="scroll" action="this._updateScrollButtonsDisabledState()"/>