"Bug 414864: don't add elements to a toolbar if they already exist in the

document, patch by Dao Gottwald <dao@mozilla.com>, r=me, a=beltzner"

toolkit/content/widgets/toolbar.xml

@@ -223,6 +223,8 @@
               newItem.id = "spacer" + uniqueId;
               newItem.className = "chromeclass-toolbar-additional";
             } else if (this.parentNode.localName == "toolbox") {
+              if (document.getElementById(aId))
+                return false;
               // Attempt to locate an item with a matching id within palette.
               var paletteItem = this.parentNode.palette.firstChild;
               while (paletteItem) {