adding HtmlEscape to dart:convert

tests/lib/convert/html_escape_test.dart

+// Copyright (c) 2013, 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.
+
+import "package:expect/expect.dart";
+import 'dart:async';
+import 'dart:convert';
+
+const _TEST_INPUT = 'A <test> of \u00A0 "double" & \'single\' values';
+
+const _OUTPUT_UNKNOWN = 'A &lt;test&gt; of &nbsp; &quot;double&quot; &amp; '
+  '&apos;single&apos; values';
+
+// const _ATTRIBUTE_MODE = "A <test> of &nbsp; &quot;double&double; and 'single' values";
+
+void main() {
+  testDefault();
+  testChunkedConvert(_OUTPUT_UNKNOWN);
+}
+
+void testDefault() {
+  var output = HTML_ESCAPE.convert(_TEST_INPUT);
+  Expect.equals(_OUTPUT_UNKNOWN, output);
+}
+
+void testChunkedConvert(String expected) {
+  var controller = new StreamController(sync: true);
+
+  var stream = controller.stream
+      .transform(HTML_ESCAPE);
+
+  var done = false;
+  int count = 0;
+
+  void stringData(value) {
+    Expect.equals(expected, value);
+    count++;
+  }
+
+  void streamClosed() {
+    done = true;
+  }
+
+  stream.listen(
+      stringData,
+      onDone: streamClosed);
+
+
+  for(var i = 0; i < _COUNT; i++) {
+    controller.add(_TEST_INPUT);
+  }
+  controller.close();
+  Expect.isTrue(done);
+  Expect.equals(_COUNT, count);
+}
+
+const _COUNT = 3;