add a JsonInfoCodec class

bin/function_size_analysis.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.
 
 /// Command-line tool presenting how much each function contributes to the total
 /// code.
 library compiler.tool.live_code_size_analysis;
 
 import 'dart:convert';
 import 'dart:io';
 import 'dart:math' as math;
 
 import 'package:dart2js_info/info.dart';
 import 'package:dart2js_info/src/graph.dart';
 import 'package:dart2js_info/src/util.dart';
 
 main(args) {
   var json = JSON.decode(new File(args[0]).readAsStringSync());
-  var info = new AllInfo.fromJson(json);
+  var info = new AllInfoJsonCodec().decode(json);
   showCodeDistribution(info);
 }
 
 showCodeDistribution(AllInfo info,
     {bool filter(Info info), bool showLibrarySizes: false}) {
   var realTotal = info.program.size;
   if (filter == null) filter = (i) => true;
   var reported = []
     ..addAll(info.functions.where(filter))
     ..addAll(info.fields.where(filter));
@@ skipping 127 matching lines @@
 
 _showElement(String name, int size, int dominatedSize, int maxSize, int total) {
   var percent = (size * 100 / total).toStringAsFixed(2);
   var minPercent = (dominatedSize * 100 / total).toStringAsFixed(2);
   var maxPercent = (maxSize * 100 / total).toStringAsFixed(2);
   print('${pad(size, 8)} ${pad(percent, 6)}% '
       '${pad(dominatedSize, 10)} ${pad(minPercent, 6)}% '
       '${pad(maxSize, 10)} ${pad(maxPercent, 6)}% '
       '$name');
 }