Fix issues that broke editing on browsers without Shadow DOM support.

dart/site/try/src/decoration.dart

Index: dart/site/try/src/decoration.dart
diff --git a/dart/site/try/src/decoration.dart b/dart/site/try/src/decoration.dart
index 663aeea44ea909bb155541f89399a3c865e76097..994a3dd62a1bb3417362c9aeb03ad103b6b34fff 100644
--- a/dart/site/try/src/decoration.dart
+++ b/dart/site/try/src/decoration.dart
@@ -9,6 +9,9 @@ import 'dart:html';
 import 'shadow_root.dart' show
     setShadowRoot;
 
+import 'editor.dart' show
+    diagnostic;
+
 class Decoration {
   final String color;
   final bool bold;
@@ -65,11 +68,7 @@ class DiagnosticDecoration extends Decoration {
     if (kind == 'error') {
       tip = error(message);
     }
-    return element..append(
-        new AnchorElement()
-            ..classes.add('diagnostic')
-            ..nodes.addAll(nodes)
-            ..append(tip));
+    return element..append(diagnostic(nodes, tip));
   }
 }