Initial GUI for review

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

Index: runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/json_view.dart
diff --git a/runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/json_view.dart b/runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/json_view.dart
new file mode 100644
index 0000000000000000000000000000000000000000..96053c75b16f83072ada19fa6b786210f479e900
--- /dev/null
+++ b/runtime/bin/vmservice/client/observatory/packages/observatory/src/observatory_elements/json_view.dart
@@ -0,0 +1,53 @@
+library json_view_element;
+
+import 'package:polymer/polymer.dart';
+import 'package:observatory/observatory.dart';
+
+@CustomTag('json-view')
+class JsonViewElement extends ObservatoryElement {
+  @observable
+  var json = null;
+  var _count = 0;
+
+  JsonViewElement() : super() {
+    bindProperty(this, const Symbol('json'), () {
+      _count = 0;
+      notifyProperty(this, const Symbol('valueType'));
+    });
+  }
+
+  String get primitiveString {
+    return json.toString();
+  }
+
+  String get valueType {
+    if (json is Map) {
+      return 'Map';
+    } else if (json is List) {
+      return 'List';
+    }
+    return 'Primitive';
+  }
+
+  int get counter {
+    return _count++;
+  }
+
+  List get list {
+    if (json is List) {
+      return json;
+    }
+    return [];
+  }
+
+  List get keys {
+    if (json is Map) {
+      return json.keys.toList();
+    }
+    return [];
+  }
+
+  dynamic value(String key) {
+    return json[key];
+  }
+}