Add <eval-link> - a custom element for evaluating an expression.

runtime/bin/vmservice/client/lib/src/elements/eval_link.dart

Index: runtime/bin/vmservice/client/lib/src/elements/eval_link.dart
diff --git a/runtime/bin/vmservice/client/lib/src/elements/eval_link.dart b/runtime/bin/vmservice/client/lib/src/elements/eval_link.dart
new file mode 100644
index 0000000000000000000000000000000000000000..be08b76237e2ea09cad27386b3e241f3225ea821
--- /dev/null
+++ b/runtime/bin/vmservice/client/lib/src/elements/eval_link.dart
@@ -0,0 +1,33 @@
+// 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 eval_link_element;
+
+import 'package:observatory/service.dart';
+import 'package:polymer/polymer.dart';
+
+@CustomTag('eval-link')
+class EvalLinkElement extends PolymerElement {
+  EvalLinkElement.created() : super.created();
+
+  @observable bool busy = false;
+  @published var callback = null;
+  @published String expr = '';
+  @published ServiceObject result = null;
+
+  void evalNow(var a, var b, var c) {
+    if (busy) {
+      return;
+    }
+    if (callback != null) {
+      busy = true;
+      result = null;
+      callback(expr).then((ServiceObject obj) {
+          result = obj;
+        }).whenComplete(() {
+          busy = false;
+        });
+    }
+  }
+}