An empty .results file would throw ValueError, eat it.

tools/isolate/isolate_smoke_test.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import cStringIO
 import hashlib
 import json
 import logging
 import os
@@ skipping 460 matching lines @@
       self.fail()
     except subprocess.CalledProcessError, e:
       out = e.output
     self._expect_no_tree()
     self._expect_results(['fail.py'], None, None)
     expected = 'Failing'
     if sys.platform == 'win32':
       # Includes spew from tracerpt.exe.
       self.assertTrue(out.startswith(expected))
     else:
-      self.assertEquals(expected, out.rstrip())
+      lines = out.strip().splitlines()
+      self.assertEquals(3, len(lines))
+      self.assertTrue(lines[0].startswith('WARNING'))
+      self.assertTrue(lines[1].startswith('WARNING'))
+      self.assertEquals(expected, lines[2])
 
   def test_missing_trailing_slash(self):
     try:
       self._execute('trace', 'missing_trailing_slash.isolate', [], True)
       self.fail()
     except subprocess.CalledProcessError, e:
       out = e.output
     self._expect_no_tree()
     self._expect_no_result()
     expected = (
@@ skipping 207 matching lines @@
     # Clean the directory from the logs, which are OS-specific.
     isolate.trace_inputs.get_api().clean_trace(
         os.path.join(self.tempdir, 'isolate_smoke_test.results.log'))
     self.assertEquals(files, list_files_tree(self.tempdir))
 
 
 if __name__ == '__main__':
   VERBOSE = '-v' in sys.argv
   logging.basicConfig(level=logging.DEBUG if VERBOSE else logging.ERROR)
   unittest.main()