Roll Observatory packages and add a roll script

packages/petitparser/test/dart_file_tests.dart

+/// This test-case automatically generates various tests from Dart source
+/// code. Unfortunately the parser is currently unable to parse most of
+/// these files.
+library petitparser.test.dart_file_test;
+
+import 'dart:io';
+
+import 'package:test/test.dart';
+
+import 'package:petitparser/dart.dart';
+import 'package:petitparser/test.dart';
+
+void generateTests(DartGrammar dart, String title, List<FileSystemEntity> files) {
+  group(title, () {
+    files
+        .where((file) => file is File && file.path.endsWith('.dart'))
+        .forEach((File file) {
+          test(file.path, () {
+            var source = new StringBuffer();
+            file
+                .openRead()
+                .transform(SYSTEM_ENCODING.decoder)
+                .listen((part) => source.write(part), onDone: expectAsync(() {
+                  expect(source.toString(), accept(dart));
+                }), onError: fail);
+          });
+        });
+  });
+}
+
+void main() {
+  var dart = new DartGrammar();
+  generateTests(dart, 'Dart SDK', new Directory('packages')
+      .listSync(recursive: true, followLinks: false));
+  generateTests(dart, 'PetitParser', Directory.current
+      .listSync(recursive: true, followLinks: true));
+}