Fix flaky tests on chromium buildbot, by adding a correct fix to test.dart.

tools/testing/dart/test_runner.dart

 // 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.
 
 #library("test_runner");
 
 #import("status_file_parser.dart");
 #import("test_progress.dart");
 #import("test_suite.dart");
 
@@ skipping 133 matching lines @@
       return (!timedOut && (exitCode < 0) && ((0x3FFFFF00 & exitCode) == 0));
     }
     // The Java dartc runner exits with code 253 in case of unhandled
     // exceptions.
     return (!timedOut && ((exitCode < 0) || (exitCode == 253)));
   }
 
   bool get hasTimedOut() => timedOut;
 
   bool get didFail() {
-    if (exitCode != 0 && !hasCrashed) return true;
+    if (testCase is !BrowserTestCase) return (exitCode != 0 && !hasCrashed);
 
+    // Browser case:
     // Browser tests fail unless stdout contains
     // 'Content-Type: text/plain\nPASS'.
-    if (testCase is !BrowserTestCase) return false;
     String previous_line = '';
     for (String line in stdout) {
       if (line == 'PASS' && previous_line == 'Content-Type: text/plain') {
-        return false;
+        return (exitCode != 0 && !hasCrashed);
       }
       // If the browser test failed, it may have been because DumpRenderTree
-      // and the virtual framebuffer X server didn't hook up.  So return false
-      // if we get the X server error.  Issue dart:1135 is filed.
+      // and the virtual framebuffer X server didn't hook up.
       if (line.contains('Gtk-WARNING **: cannot open display: :99')) {

[Siggi Cherem (dart-lang), 2012/01/11 20:55:15]

I just saw the failure here:
http://chromegw.corp.google.com/i/client.dash/builders/frogium-linux-debug/bu...

I believe the problem is that this error shows in stderr, rather than stdout.
I'll be happy to send you a fix.

-        return false;
+        // If we get the X server error, return the expected value
+        // We cannot restart the test from here.  Issue dart:1135 is filed.
+        return testCase.isNegative;

[Siggi Cherem (dart-lang), 2012/01/11 18:40:15]

could we print a warning to stdout too?

       }
       previous_line = line;
     }
     return true;
   }
 
   // Reverse result of a negative test.
   bool get hasFailed() => (testCase.isNegative ? !didFail : didFail);
 }
 
@@ skipping 321 matching lines @@
           test.displayName != 'dartc/junit_tests') {
         _ensureDartcBatchRunnersStarted(test.executablePath);
         _getDartcBatchRunnerProcess().startTest(test);
       } else {
         new RunningProcess(test).start();
       }
       _numProcesses++;
     }
   }
 }