add tool to get breakdown of deferred libraries by size

bin/code_deps.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 to query for code dependencies. Currently this tool only
 /// supports the `some_path` query, which gives you the shortest path for how
 /// one function depends on another.
 ///
 /// You can run this tool as follows:
 /// ```bash
 /// pub global activate dart2js_info
 /// dart2js_info_code_deps out.js.info.json some_path main foo
 /// ```
 ///
 /// The arguments to the query are regular expressions that can be used to
 /// select a single element in your program. If your regular expression is too
 /// general and has more than one match, this tool will pick
 /// the first match and ignore the rest. Regular expressions are matched against
 /// a fully qualified element name, which includes the library and class name
 /// (if any) that contains it. A typical qualified name is of this form:
 ///
 ///     libraryName::ClassName.elementName
 ///
 /// If the name of a function your are looking for is unique enough, it might be
 /// sufficient to just write that name as your regular expression.
 library dart2js_info.bin.code_deps;
 
 import 'dart:collection';
-import 'dart:convert';
 import 'dart:io';
 
 import 'package:dart2js_info/info.dart';
 import 'package:dart2js_info/src/graph.dart';
 import 'package:dart2js_info/src/util.dart';
 
-main(args) {
+main(args) async {
   if (args.length < 2) {
     print('usage: dart2js_info_code_deps path-to.info.json <query>');
     print('   where <query> can be:');
     print('     - some_path <element-regexp-1> <element-regexp-2>');
     // TODO(sigmund): add other queries, such as 'all_paths'.
     exit(1);
   }
 
-  var json;
-  try {
-    json = JSON.decode(new File(args[0]).readAsStringSync());
-  } catch (e) {
-    print('error: could not read ${args[0]}');
-    exit(1);
-  }
-  var info = new AllInfoJsonCodec().decode(json);
+  var info = await infoFromFile(args.first);
   var graph = graphFromInfo(info);
 
   var queryName = args[1];
   if (queryName == 'some_path') {
     if (args.length < 4) {
       print('missing arguments for `some_path`');
       exit(1);
     }
     var source = info.functions
         .firstWhere(_longNameMatcher(new RegExp(args[2])), orElse: () => null);
@@ skipping 57 matching lines @@
         if (seen.containsKey(neighbor)) continue;
         seen[neighbor] = node;
         queue.addLast(neighbor);
       }
     }
     return [];
   }
 }
 
 _longNameMatcher(RegExp regexp) => (e) => regexp.hasMatch(longName(e));