Add a JSON reporter.

lib/src/runner/configuration.dart

 // Copyright (c) 2015, 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.
 
 library test.runner.configuration;
 
 import 'dart:io';
 import 'dart:math' as math;
 
 import 'package:args/args.dart';
@@ skipping 47 matching lines @@
         help: 'The port of a pub serve instance serving "test/".',
         valueHelp: 'port');
     parser.addFlag("pause-after-load",
         help: 'Pauses for debugging before any tests execute.\n'
             'Implies --concurrency=1.\n'
             'Currently only supported for browser tests.',
         negatable: false);
     parser.addOption("reporter",
         abbr: 'r',
         help: 'The runner used to print test results.',
-        allowed: ['compact', 'expanded'],
+        allowed: ['compact', 'expanded', 'json'],
         defaultsTo: Platform.isWindows ? 'expanded' : 'compact',
         allowedHelp: {
       'compact': 'A single line, updated continuously.',
-      'expanded': 'A separate line for each update.'
+      'expanded': 'A separate line for each update.',
+      'json': 'A machine-readable format (see https://goo.gl/0HRhdZ).'
     });
     parser.addFlag("verbose-trace", negatable: false,
         help: 'Whether to emit stack traces with core library frames.');
     parser.addFlag("js-trace", negatable: false,
         help: 'Whether to emit raw JavaScript stack traces for browser tests.');
     parser.addFlag("color", defaultsTo: null,
         help: 'Whether to use terminal colors.\n(auto-detected by default)');
 
     return parser;
   })();
@@ skipping 118 matching lines @@
         pubServeUrl = pubServePort == null
             ? null
             : Uri.parse("http://localhost:$pubServePort"),
         concurrency = pauseAfterLoad
             ? 1
             : (concurrency == null ? _defaultConcurrency : concurrency),
         platforms = platforms == null ? [TestPlatform.vm] : platforms.toList(),
         paths = paths == null ? ["test"] : paths.toList(),
         explicitPaths = paths != null;
 }