bug 169378 - first Firefox window is ignored by window mediator - causing windows opened before the DOM inspector is opened to not appear in the DOM inspector's window list. This is fixed by initializing the window datasource after the first window is shown, when the DOM inspector is installed.

browser/extensions/inspector/content/tasksOverlay.xul

@@ -6,6 +6,26 @@
          xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
 
   <script type="application/x-javascript" src="chrome://inspector/content/hooks.js"/>
+  
+  <script type="application/x-javascript">
+  <![CDATA[
+    function inspectorWindowLoad()
+    {
+      setTimeout("initWindowMediator()", 0);
+    }
+    
+    function initWindowMediator()
+    {
+      // Load the Window DataSource so that browser windows opened subsequent to DOM
+      // Inspector show up in the DOM Inspector's window list.
+      var windowDS = Components.classes["@mozilla.org/rdf/datasource;1?name=window-mediator"]
+                               .getService(Components.interfaces.nsIWindowDataSource);
+    }
+  
+    window.addEventListener("load", inspectorWindowLoad, false);
+  
+  ]]>
+  </script>
 
   <commandset id="mainCommandSet">
     <command id="Tasks:Inspector" oncommand="inspectDOMDocument();"/>