Fix reuse of <ref> elements

runtime/observatory/lib/src/elements/observatory_element.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 observatory_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'package:observatory/app.dart';
 import 'package:observatory/service.dart';
@@ skipping 146 matching lines @@
     if (wasTruncated) {
       result.addAll("...".codeUnits);
     } else {
       result.add("'".codeUnitAt(0));
     }
     return new String.fromCharCodes(result);
   }
 
   void clearShadowRoot() {
     // Remove all non-style elements.
-    shadowRoot.children.removeWhere((e) => e is! StyleElement);
+    // Have to do the following because removeWhere doesn't work on DOM child
+    // node lists. i.e. removeWhere((e) => e is! StyleElement);
+    var styleElements = [];
+    for (var child in shadowRoot.children) {
+      if (child is StyleElement) {
+        styleElements.add(child);
+      }
+    }
+    shadowRoot.children.clear();
+    for (var style in styleElements) {
+      shadowRoot.children.add(style);
+    }
   }
 
   void insertTextSpanIntoShadowRoot(String text) {
     var spanElement = new SpanElement();
     spanElement.text = text;
     shadowRoot.children.add(spanElement);
   }
 
   void insertLinkIntoShadowRoot(String label, String href, [String title]) {
     var anchorElement = new AnchorElement();
     anchorElement.href = href;
     anchorElement.text = label;
     if (title != null) {
       anchorElement.title = title;
     }
     anchorElement.onClick.listen(onClickGoto);
     shadowRoot.children.add(anchorElement);
   }
 }