Converting Polymer's WebComponentsLoaded to an onReady future

pkg/polymer/lib/src/loader.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;
 
 /** Annotation used to automatically register polymer elements. */
 class CustomTag {
   final String tagName;
   const CustomTag(this.tagName);
@@ skipping 24 matching lines @@
         (_) => performMicrotaskCheckpoint());
 
     // TODO(jmesserly): mdv should use initMdv instead of mdv.initialize.
     mdv.initialize();
     document.register(PolymerDeclaration._TAG, PolymerDeclaration);
 
     for (var lib in libraries) {
       _loadLibrary(lib, srcUrl);
     }
 
-    // TODO(jmesserly): this should be in the custom_element polyfill, not here.
-    // notify the system that we are bootstrapped
-    document.body.dispatchEvent(
-        new CustomEvent('WebComponentsReady', canBubble: true));
+    Polymer._ready.complete();
+
+    // TODO(sigmund): move to boot.dart once it's ready.
+    document.body.style.transition = 'opacity 0.3s';
+    document.body.style.opacity = '1';
   });
 }
 
 /** All libraries in the current isolate. */
 final _libs = currentMirrorSystem().libraries;
 
 /**
  * Reads the library at [uriString] (which can be an absolute URI or a relative
  * URI from [srcUrl]), and:
  *
@@ skipping 82 matching lines @@
     print("warning: methods marked with @initMethod should take no "
         "arguments, ${method.simpleName} expects some.");
     return;
   }
   obj.invoke(method.simpleName, const []);
 }
 
 class _InitMethodAnnotation {
   const _InitMethodAnnotation();
 }