introduce web_components pkg for consolidated polyfills

pkg/polymer/lib/src/declaration.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.
 
 part of polymer;
 
 /**
  * **Warning**: this class is experiental and subject to change.
  *
  * The implementation for the `polymer-element` element.
@@ skipping 640 matching lines @@
 const _STYLE_SCOPE_ATTRIBUTE = 'element';
 const _STYLE_CONTROLLER_SCOPE = 'controller';
 
 String _cssTextFromSheet(LinkElement sheet) {
   if (sheet == null) return '';
 
   // TODO(jmesserly): sometimes the href property is wrong after deployment.
   var href = sheet.href;
   if (href == '') href = sheet.attributes["href"];
 
+  // TODO(jmesserly): our build is not doing the right thing for
+  // link rel=stylesheet, see http://dartbug.com/16648
   if (js.context != null && js.context.hasProperty('HTMLImports')) {
     var jsSheet = new js.JsObject.fromBrowserObject(sheet);
     var resource = jsSheet['__resource'];
     if (resource != null) return resource;
-    _sheetLog.fine('failed to get stylesheet text href="$href"');
-    return '';
+    // TODO(jmesserly): figure out why HTMLImports is failing to load these.
+    // Falling back to sync XHR is no good.
+    // _sheetLog.fine('failed to get stylesheet text href="$href"');
+    // return '';
   }
   // TODO(jmesserly): it seems like polymer-js is always polyfilling
   // HTMLImports, because their code depends on "__resource" to work.
   // We work around this by using a sync XHR to get the stylesheet text.
   // Right now this code is only used in Dartium, but if it's going to stick
   // around we will need to find a different approach.
   try {
     return (new HttpRequest()
         ..open('GET', href, async: false)
         ..send())
@@ skipping 45 matching lines @@
 
 // Dart note: we need this function because we have additional renames JS does
 // not have. The JS renames are simply case differences, whereas we have ones
 // like doubleclick -> dblclick and stripping the webkit prefix.
 String _eventNameFromType(String eventType) {
   final result = _reverseEventTranslations[eventType];
   return result != null ? result : eventType;
 }
 
 final _ATTRIBUTES_REGEX = new RegExp(r'\s|,');