move html5lib code into dart svn repo

pkg/third_party/html5lib/test/dom_compat_test.dart

+library dom_compat_test;
+
+import 'dart:async';
+import 'dart:io';
+import 'package:unittest/unittest.dart';
+import 'package:unittest/compact_vm_config.dart';
+import 'package:html5lib/dom.dart';
+
+part 'dom_compat_test_definitions.dart';
+
+main() {
+  useCompactVMConfiguration();
+
+  registerDomCompatTests();
+
+  test('content_shell', () {
+    _runDrt('test/browser/browser_test.html');
+  });
+}
+
+void _runDrt(String htmlFile) {
+  final allPassedRegExp = new RegExp('All \\d+ tests passed');
+
+  final future = Process.run('content_shell', ['--dump-render-tree', htmlFile])
+    .then((ProcessResult pr) {
+      expect(pr.exitCode, 0);
+      expect(pr.stdout, matches(allPassedRegExp), reason: pr.stdout);
+    });
+
+  expect(future, completion(isNull));
+}