Move the status file parser into its own package.

pkg/status_file/lib/expectation.dart

 // Copyright (c) 2017, 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.
 
 /// The possible outcomes from running a test.
 class Expectation {
   /// The test completed normally and did what it intended to do.
   static final Expectation pass = new Expectation._('Pass');
 
   /// The process aborted in a way that is not a potential runtime error coming
@@ skipping 191 matching lines @@
         return true;
       }
       outcome = outcome._group;
     }
 
     return false;
   }
 
   String toString() => _name;
 }