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

tools/isolate/isolate.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.
 
 """Does one of the following depending on the --mode argument:
   check     Verifies all the inputs exist, touches the file specified with
             --result and exits.
   hashtable Puts a manifest file and hard links each of the inputs into the
             output directory.
@@ skipping 280 matching lines @@
     return out
 
   @classmethod
   def load_file(cls, filename):
     """Loads the data from a file or return an empty instance."""
     out = cls()
     try:
       with open(filename, 'r') as f:
         out = cls.load(json.load(f))
       logging.debug('Loaded %s(%s)' % (cls.__name__, filename))
-    except IOError:
-      pass
+    except (IOError, ValueError):
+      logging.warn('Failed to load %s' % filename)
     return out
 
 
 class Result(Flattenable):
   """Describes the content of a .result file.
 
   This file is used by run_test_from_archive.py so its content is strictly only
   what is necessary to run the test outside of a checkout.
   """
   MEMBERS = (
@@ skipping 435 matching lines @@
       result_file,
       input_file,
       options.mode,
       variables,
       out_dir,
       parser.error)
 
 
 if __name__ == '__main__':
   sys.exit(main())