add 'imports' field for OutputUnitInfo

lib/json_info_codec.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.
 
 /// Converters and codecs for converting between JSON and [Info] classes.
 part of dart2js_info.info;
 
 // TODO(sigmund): add unit tests.
 class JsonToAllInfoConverter extends Converter<Map, AllInfo> {
   Map<String, Info> registry;
@@ skipping 42 matching lines @@
     result.program = parseProgram(json['program']);
     // todo: version, etc
     return result;
   }
 
   OutputUnitInfo parseOutputUnit(Map json) {
     OutputUnitInfo result = parseId(json['id']);
     result
       ..name = json['name']
       ..size = json['size'];
+    result.imports.addAll(json['imports'] ?? const []);
     return result;
   }
 
   LibraryInfo parseLibrary(Map json) {
     LibraryInfo result = parseId(json['id']);
     result
       ..name = json['name']
       ..uri = Uri.parse(json['canonicalUri'])
       ..outputUnit = parseId(json['outputUnit'])
       ..size = json['size'];
@@ skipping 336 matching lines @@
         'code': info.code,
         'type': info.type,
         'measurements': _visitMeasurements(info.measurements),
         // Note: version 3.2 of dump-info serializes `uses` in a section called
         // `holding` at the top-level.
       });
   }
 
   visitTypedef(TypedefInfo info) => _visitBasicInfo(info)..['type'] = info.type;
 
-  visitOutput(OutputUnitInfo info) => _visitBasicInfo(info);
+  visitOutput(OutputUnitInfo info) =>
+      _visitBasicInfo(info)..['imports'] = info.imports;
 }
 
 class AllInfoJsonCodec extends Codec<AllInfo, Map> {
   final Converter<AllInfo, Map> encoder = new AllInfoToJsonConverter();
   final Converter<Map, AllInfo> decoder = new JsonToAllInfoConverter();
 }