Initial GUI for review

runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/message_viewer.dart

Index: runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/message_viewer.dart
diff --git a/runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/message_viewer.dart b/runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/message_viewer.dart
new file mode 100644
index 0000000000000000000000000000000000000000..378bd04a6ff70ccf0dbbb8a3b2e0a4e5262e51f8
--- /dev/null
+++ b/runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/message_viewer.dart
@@ -0,0 +1,30 @@
+library message_viewer_element;
+
+import 'package:polymer/polymer.dart';
+import 'package:observatory/observatory.dart';
+
+@CustomTag('message-viewer')
+class MessageViewerElement extends ObservatoryElement {
+  Map _message;
+  Map get message => _message;
+
+  set message(Map m) {
+    _message = m;
+    notifyProperty(this, const Symbol('messageType'));
+    notifyProperty(this, const Symbol('members'));
+  }
+
+  String get messageType {
+    if (message == null || message['type'] == null) {
+      return 'Error';
+    }
+    return message['type'];
+  }
+
+  List<Map> get members {
+    if (message == null || message['members'] == null) {
+      return [];
+    }
+    return message['members'];
+  }
+}