Attempt to fix timeout of failing selenium tests.

dart/pkg/unittest/test_controller.js

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Test controller logic - used by unit test harness to embed tests in
  * DumpRenderTree.
  */
 
 if (navigator.webkitStartDart) {
@@ skipping 91 matching lines @@
   }
   var pre = document.createElement("pre");
   pre.appendChild(document.createTextNode(String(msg)));
   document.body.appendChild(pre);
 }
 
 // dart2js will generate code to call this function instead of calling
 // Dart [main] directly. The argument is a closure that invokes main.
 function dartMainRunner(main) {
   window.postMessage('dart-calling-main', '*');
-  main();
+  try {
+    main();
+  } catch (e) {
+    showErrorAndExit(String(e));
+  }
   window.postMessage('dart-main-done', '*');
 }