Move computation of method flags into model.

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';
 
 import 'analyze_helper.dart';
 
 // Do not remove WHITE_LIST even if it's empty.  The error message for
 // unused members refers to WHITE_LIST by name.
 const Map<String, List<String>> WHITE_LIST = const {
   // Helper methods for debugging should never be called from production code:
   "lib/src/helpers/": const [" is never "],
 
-  // Hack to give try private access:
-  "lib/src/js_emitter/program_builder.dart": const [
-      "The method 'buildClassWithFieldsForTry' is never called"],
-
   // Node.asLiteralBool is never used.
   "lib/src/tree/nodes.dart": const [
       "The method 'asLiteralBool' is never called"],
 
   // Some things in dart_printer are not yet used
   "lib/src/dart_backend/backend_ast_nodes.dart": const [" is never "],
 
   // MethodElement
   // TODO(20377): Why is MethodElement unused?
   "lib/src/elements/elements.dart": const [" is never "]
@@ skipping 25 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();
 }