add tool to get breakdown of deferred libraries by size

bin/deferred_library_check.dart

Index: bin/deferred_library_check.dart
diff --git a/bin/deferred_library_check.dart b/bin/deferred_library_check.dart
index d9cd15115b6be8f7ed538a7a884efd98e1fff0d8..19cceefdc3005a55f4d8863cf15e0e394597caa3 100644
--- a/bin/deferred_library_check.dart
+++ b/bin/deferred_library_check.dart
@@ -36,11 +36,10 @@
 library dart2js_info.bin.deferred_library_check;
 
 import 'dart:async';
-import 'dart:convert';
 import 'dart:io';
 
-import 'package:dart2js_info/info.dart';
 import 'package:dart2js_info/deferred_library_check.dart';
+import 'package:dart2js_info/src/util.dart';
 import 'package:yaml/yaml.dart';
 
 Future main(List<String> args) async {
@@ -56,11 +55,6 @@ Future main(List<String> args) async {
   if (failures.isNotEmpty) exitCode = 1;
 }
 
-Future<AllInfo> infoFromFile(String fileName) async {
-  var file = await new File(fileName).readAsString();
-  return new AllInfoJsonCodec().decode(JSON.decode(file));
-}
-
 Future manifestFromFile(String fileName) async {
   var file = await new File(fileName).readAsString();
   return loadYaml(file);