Add new <curly-block> element.

runtime/bin/vmservice/client/lib/src/observatory_elements/curly_block.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.
+
+library curly_block_element;
+
+import 'package:logging/logging.dart';
+import 'package:polymer/polymer.dart';
+
+@CustomTag('curly-block')
+class CurlyBlockElement extends PolymerElement {
+  CurlyBlockElement.created() : super.created();
+
+  @observable bool expanded = false;
+  @observable bool busy = false;
+  @published var callback = null;
+
+  void doneCallback() {
+    print("done callback");
+    expanded = !expanded;
+    busy = false;
+  }
+
+  void toggleExpand(var a, var b, var c) {
+    if (busy) {
+      return;
+    }
+    if (callback != null) {
+      busy = true;
+      callback(!expanded, doneCallback);
+    } else {
+      expanded = !expanded;
+    }
+  }
+}