Bug 540529 - disable tree/test_tabbrowser.xul on linux

accessible/tests/mochitest/tree/test_tabbrowser.xul

@@ -37,6 +37,14 @@
 
     function doTest()
     {
+      if (LINUX) {
+        // XXX: bug 540529
+
+        todo(false, "Failure on Linux.");
+        SimpleTest.finish();
+        return;
+      }
+
       var tabBrowser = document.getElementById("tabbrowser");
 
       var progressListener =