Add location information to the JSON reporter.

lib/src/runner.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.
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:async/async.dart';
 
 import 'backend/group.dart';
@@ skipping 71 matching lines @@
             engine,
             color: config.color,
             verboseTrace: config.verboseTrace,
             printPath: config.paths.length > 1 ||
                 new Directory(config.paths.single).existsSync(),
             printPlatform: config.platforms.length > 1);
         break;
 
       case "json":
         reporter = JsonReporter.watch(engine,
-            verboseTrace: config.verboseTrace);
+            verboseTrace: config.verboseTrace, jsLocations: !config.jsTrace);
         break;
     }
 
     return new Runner._(config, loader, engine, reporter);
   }
 
   Runner._(this._config, this._loader, this._engine, this._reporter);
 
   /// Starts the runner.
   ///
@@ skipping 271 matching lines @@
       await _debugOperation.valueOrCancellation();
     }).listen(null);
 
     var results = await Future.wait([
       _suiteSubscription.asFuture().then((_) => _engine.suiteSink.close()),
       _engine.run()
     ]);
     return results.last;
   }
 }