Move all main methods to tool/.

pkg/front_end/lib/src/fasta/parser/parser_main.dart

 // Copyright (c) 2016, 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 fasta.parser.main;
 
 import 'dart:convert' show LineSplitter, UTF8;
 
 import 'dart:io' show File;
 
@@ skipping 12 matching lines @@
 class DebugListener extends Listener {
   void handleIdentifier(Token token, IdentifierContext context) {
     logEvent("Identifier: ${token.value}");
   }
 
   void logEvent(String name) {
     print(name);
   }
 }
 
-main(List<String> arguments) async {
+mainEntryPoint(List<String> arguments) async {
   for (String argument in arguments) {
     if (argument.startsWith("@")) {
       Uri uri = Uri.base.resolve(argument.substring(1));
       await for (String file in new File.fromUri(uri)
           .openRead()
           .transform(UTF8.decoder)
           .transform(const LineSplitter())) {
         outLine(uri.resolve(file));
       }
     } else {
       outLine(Uri.base.resolve(argument));
     }
   }
 }
 
 void outLine(Uri uri) {
   new TopLevelParser(new DebugListener())
       .parseUnit(scan(readBytesFromFileSync(uri)).tokens);
 }