Converted Observatory nav-refresh element

runtime/observatory/lib/src/elements/nav/refresh_wrapper.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 file.
+
+import 'dart:html';
+import 'dart:async';
+
+import 'package:observatory/app.dart';
+import 'package:observatory/src/elements/helpers/tag.dart';
+import 'package:observatory/src/elements/shims/binding.dart';
+import 'package:observatory/src/elements/nav/refresh.dart';
+
+class NavRefreshElementWrapper extends HtmlElement {
+  static final binder = new Binder<NavRefreshElementWrapper>(
+    const [const Binding('callback'), const Binding('label')]);
+
+  static const tag = const Tag<NavRefreshElementWrapper>('nav-refresh');
+
+  Function _callback;
+  String _label = 'Refresh';
+  Function get callback => _callback;
+  String get label => _label;
+  set callback(Function value) {
+    _callback = value; render();
+  }

[rmacnak, 2016/07/19 00:13:33]

Some labels don't seem to make it here. For example, the allocation profile page
now displays three buttons all labelled 'Refresh'.

[cbernaschina, 2016/07/19 02:56:07]

done

The bug was at line 32.
I misunderstood the meaning of the ??= operator.
Changed in:
_label = getAttribute('label') ?? 'Refresh';

+  set label(String value) {
+    _label = value; render();
+  }
+
+  NavRefreshElementWrapper.created() : super.created() {
+    binder.registerCallback(this);
+    _label ??= getAttribute('label');
+    createShadowRoot();
+    render();
+  }
+
+  @override
+  void attached() {
+    super.attached();
+    render();
+  }
+
+  void render() {
+    shadowRoot.children = [];
+    if (_callback == null || _label == null) return;
+
+    shadowRoot.children = [
+      new StyleElement()
+        ..text = '''nav-refresh-wrapped > li > button {
+          color: #000;
+          margin: 3px;
+          padding: 8px;
+          border-width: 2px;
+          line-height: 13px;
+          font: 400 13px 'Montserrat', sans-serif;
+        }
+        nav-refresh-wrapped > li > button[disabled] {
+          color: #aaa;
+          cursor: wait;
+        }
+        nav-refresh-wrapped > li {
+          float: right;
+          margin: 0;
+        }''',
+      new NavRefreshElement(label: _label,
+                            queue: ObservatoryApplication.app.queue)
+        ..onRefresh.listen((event) async{
+          event.element.disabled = true;
+          try {
+            var future = callback();
+            if (future is Future) await future;
+          } finally {
+            event.element.disabled = false;
+          }
+        })
+    ];
+  }
+}