Don't wait unnecessarily.

tests/stub-generator/testcfg.py

 # 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.
 
 import os
 import re
 import shutil
 import sys
 import tempfile
 
@@ skipping 21 matching lines @@
   def GetStubs(self):
     source = self.GetSource()
     stub_classes = utils.ParseTestOptions(test.ISOLATE_STUB_PATTERN, source,
                                           self.context.workspace)
     if stub_classes is None:
       return (None, None, None)
     (interface, _, classes) = stub_classes[0].partition(':')
     (interface, _, implementation) = interface.partition('+')
     return (interface, classes, implementation)
 
+  def IsFailureOutput(self, output):
+    return output.exit_code != 0 or not '##DONE##' in output.stdout
+
   def BeforeRun(self):
     if not self.context.generate:
       return
     (interface, classes, _) = self.GetStubs()
     if interface is None:
       return
     d = join(self.GetPath(), 'generated')
     if not isdir(d):
       os.mkdir(d)
     tmpdir = tempfile.mkdtemp()
@@ skipping 74 matching lines @@
                                       test_path,
                                       join(root, f),
                                       mode,
                                       arch,
                                       component))
     return tests
 
 
 def GetConfiguration(context, root):
   return DartStubTestConfiguration(context, root)