Print name of previous test when a browser test times out.

tools/testing/dart/browser_controller.dart

 // Copyright (c) 2013, 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.
 library browser;
 
 import "dart:async";
 import "dart:convert" show LineSplitter, UTF8, JSON;
 import "dart:core";
 import "dart:io";
 import "dart:math" show max, min;
@@ skipping 1074 matching lines @@
     timedOut.add(status.currentTest.url);
     var id = status.browser.id;
 
     status.currentTest.stopwatch.stop();
     status.browser.close().then((_) {
       var lastKnownMessage =
           'Dom could not be fetched, since the test timed out.';
       if (status.currentTest.lastKnownMessage.length > 0) {
         lastKnownMessage = status.currentTest.lastKnownMessage;
       }
+      if (status.lastTest != null) {
+        lastKnownMessage += '\nPrevious test was ${status.lastTest.url}';
+      }
       // Wait until the browser is closed before reporting the test as timeout.
       // This will enable us to capture stdout/stderr from the browser
       // (which might provide us with information about what went wrong).
       var browserTestOutput = new BrowserTestOutput(
           status.currentTest.delayUntilTestStarted,
           status.currentTest.stopwatch.elapsed,
           lastKnownMessage,
           status.browser.testBrowserOutput,
           didTimeout: true);
       status.currentTest.doneCallback(browserTestOutput);
@@ skipping 674 matching lines @@
     </div>
     <div id="embedded_iframe_div" class="test box">
       <iframe style="width:100%;height:100%;" id="embedded_iframe"></iframe>
     </div>
   </body>
 </html>
 """;
     return driverContent;
   }
 }