Move the status file parser into its own package.

tools/testing/dart/command_output.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.
 
 import 'dart:convert';
 // We need to use the 'io' prefix here, otherwise io.exitCode will shadow
 // CommandOutput.exitCode in subclasses of CommandOutput.
 import 'dart:io' as io;
 
+import 'package:status_file/expectation.dart';
+
 import 'browser_controller.dart';
 import 'command.dart';
 import 'configuration.dart';
-import 'expectation.dart';
 import 'test_runner.dart';
 import 'utils.dart';
 
 /// CommandOutput records the output of a completed command: the process's exit
 /// code, the standard output and standard error, whether the process timed out,
 /// and the time the process took to run. It does not contain a pointer to the
 /// [TestCase] this is the output of, so some functions require the test case
 /// to be passed as an argument.
 class CommandOutput extends UniqueObject {
   final Command command;
@@ skipping 806 matching lines @@
     // complete successfully, it's outcome is Expectation.FAIL.
     // TODO: maybe we should introduce a AsyncIncomplete marker or so
     if (outcome == Expectation.pass) {
       if (_isAsyncTest(testOutput) && !_isAsyncTestSuccessful(testOutput)) {
         return Expectation.fail;
       }
     }
     return outcome;
   }
 }