Move all main methods to tool/.

pkg/front_end/lib/src/fasta/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;
-
-import '../scanner/token.dart' show Token;
-
-import '../scanner/io.dart' show readBytesFromFileSync;
-
-import '../scanner.dart' show scan;
-
-import 'listener.dart' show Listener;
-
-import 'top_level_parser.dart' show TopLevelParser;
-
-import 'identifier_context.dart' show IdentifierContext;
-
-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 {
-  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);
-}