Move parser and token related libraries into their own subfolder.

pkg/compiler/lib/src/scanner/parser_task.dart

-// Copyright (c) 2011, 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 dart2js.parser.task;
-
-import '../common/tasks.dart' show
-    CompilerTask;
-import '../compiler.dart' show
-    Compiler;
-import '../diagnostics/invariant.dart' show
-    invariant;
-import '../elements/modelx.dart' show
-    ElementX;
-import '../tree/tree.dart' show
-    Node;
-
-import 'listener.dart' show
-    NodeListener,
-    ParserError;
-import 'parser.dart' show
-    Parser;
-import 'token.dart' show
-    Token;
-
-class ParserTask extends CompilerTask {
-  ParserTask(Compiler compiler) : super(compiler);
-  String get name => 'Parser';
-
-  Node parse(ElementX element) {
-    return measure(() => element.parseNode(compiler));
-  }
-
-  Node parseCompilationUnit(Token token) {
-    return measure(() {
-      NodeListener listener = new NodeListener(compiler, null);
-      Parser parser = new Parser(listener);
-      try {
-        parser.parseUnit(token);
-      } on ParserError catch(_) {
-        assert(invariant(token, compiler.compilationFailed));
-        return listener.makeNodeList(0, null, null, '\n');
-      }
-      Node result = listener.popNode();
-      assert(listener.nodes.isEmpty);
-      return result;
-    });
-  }
-}