Modify scanner and parser to be standalone packages.

pkg/dart_parser/lib/parser.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.md file.
+
+library parser;
+
+import 'package:scanner/src/token.dart' show

[Siggi Cherem (dart-lang), 2017/01/12 21:56:04]

It doesn't have to be done now on this CL since you likely have a pile of CLs
stacked on top of this that will have conflicts, but at some point before we
integrate into master we should run dartfmt on all the files.

It took us time to switch in dart2js, but now we really enjoy delegating
formatting to it.

[ahe, 2017/01/13 07:16:20]

The way dartfmt formats show clauses slow me down. It makes it harder to see how
show clauses have changed when reviewing code, and it makes it harder for me to
add new items.

+    Token;
+
+import 'src/listener.dart' show
+    Listener;
+
+import 'src/parser.dart' show
+    Parser;
+
+import 'src/listener.dart' show
+    ParserError;
+
+export 'src/listener.dart' show
+    ParserError;
+
+List<ParserError> parse(Token tokens, {bool enableGenericMethodSyntax: false}) {

[Siggi Cherem (dart-lang), 2017/01/12 21:56:04]

also can be done on a later CL, but the enableGenericMethodSyntax flag is now
gone and defaults to true.

[ahe, 2017/01/13 07:16:20]

Yes. I'll address this when I have landed my other changes and merge with
changes to the parser since I copied it.

+  Listener listener = new Listener();
+  Parser parser = new Parser(listener,
+      enableGenericMethodSyntax: enableGenericMethodSyntax);
+  parser.parseUnit(tokens);
+  return listener.recoverableErrors;
+}