FOUC lint test

pkg/polymer/lib/src/build/linter.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.
 
 /// Logic to validate that developers are correctly using Polymer constructs.
 /// This is mainly used to produce warnings for feedback in the editor.
 library polymer.src.build.linter;
 
 import 'dart:async';
 import 'dart:convert';
@@ skipping 375 matching lines @@
           'the custom element declaration.', span: node.sourceSpan);
       return;
     }
 
     if (hasIsAttribute && baseTag != nodeTag) {
       _logger.warning(
           'custom element "$customTagName" extends from "$baseTag". '
           'Did you mean to write <$baseTag is="$customTagName">?',
           span: node.sourceSpan);
     }
+
+    // FOUC check, if content is supplied
+    if (!node.innerHtml.isEmpty) {
+      var parent = node;
+      var hasFoucFix = false;
+      while(parent != null && !hasFoucFix) {

[Siggi Cherem (dart-lang), 2014/09/04 00:12:32]

nit: space before '('

+        if (parent.localName == 'polymer-element' ||
+            parent.attributes['unresolved'] != null) {
+          hasFoucFix = true;
+        }
+        if (parent.localName == 'body') break;
+        parent = parent.parent;
+      }
+      if (!hasFoucFix) {
+        _logger.warning(
+            'Custom element found in document body without an '
+            '"unresolved" attribute on it or one of its parents. This means '
+            'your app probably has a flash of unstyled content before it '
+            'finishes loading. See http://goo.gl/iN03Pj for more info.',
+            span: node.sourceSpan);
+      }
+    }
   }
 
   /// Validate an attribute on a custom-element. Returns true if valid.
   bool _validateCustomAttributeName(String name, FileSpan span) {
     if (name.contains('-')) {
       var newName = toCamelCase(name);
       _logger.warning('PolymerElement no longer recognizes attribute names with '
           'dashes such as "$name". Use "$newName" or "${newName.toLowerCase()}" '
           'instead (both forms are equivalent in HTML).', span: span);
       return false;
@@ skipping 58 matching lines @@
     '\'<script type="application/dart">export "package:polymer/init.dart";'
     '</script>\' or add your own script tag and call that function. '
     'Make sure the script tag is placed after all HTML imports.';
 
 const String NO_DART_SCRIPT_AND_EXPERIMENTAL =
     'The experimental bootstrap feature doesn\'t support script tags on '
     'the main document (for now).';
 
 const List<String> INTERNALLY_DEFINED_ELEMENTS = 
     const ['auto-binding-dart', 'polymer-element'];