dart2js: add visitors and parsing support to infos

tests/compiler/dart2js/analyze_unused_dart2js_test.dart

 // Copyright (c) 2013, 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.
 
 library analyze_unused_dart2js;
 
 import 'package:async_helper/async_helper.dart';
 
 import 'package:compiler/src/dart2jslib.dart';
 import 'package:compiler/src/filenames.dart';
@@ skipping 26 matching lines @@
 
   // Serialization code is only used in test.
   "lib/src/serialization/": const [
       "is never"],
 
   // Nested functions are currently kept alive in the IR.
   "lib/src/tree_ir/": const [
     "accept", "FunctionExpression", "CreateFunction"
   ],
 
+  // AllInfo.fromJson and visit methods are not used yet.
+  "lib/src/info/info.dart": const [ "is never" ],
+
   "lib/src/universe/universe.dart": const [
       "The method 'getterInvocationsByName' is never called.",
       "The method 'setterInvocationsByName' is never called."],
 
   "lib/src/cps_ir/": const [
     "accept", "CreateFunction",
   ],
 
   "/lib/src/dart_backend/backend_ast_to_frontend_ast.dart": const [
     " is never "
@@ skipping 26 matching lines @@
     } else if (member.isTypedef) {
       if (member.isResolved) {
         compiler.reportHint(member, MessageKind.GENERIC,
             {'text': "Helper typedef in production code '$member'."});
       }
     }
   }
   compiler.libraryLoader.lookupLibrary(helperUri).forEachLocalMember(checkLive);
   return handler.checkResults();
 }