update to polymer js 0.5.1

pkg/polymer/lib/src/loader.dart

Index: pkg/polymer/lib/src/loader.dart
diff --git a/pkg/polymer/lib/src/loader.dart b/pkg/polymer/lib/src/loader.dart
index ff597adc8e456541a0c5d9dd64f17f3b235a5ec2..5c40b00c253f78107d62b1cfaa509d35cc6b83ef 100644
--- a/pkg/polymer/lib/src/loader.dart
+++ b/pkg/polymer/lib/src/loader.dart
@@ -143,7 +143,9 @@ JsObject _polymerElementProto = () {
 // console automatically if any are supplied.
 void _initializeLogging() {
   hierarchicalLoggingEnabled = true;
-  var logFlags = js.context['logFlags'];
+  var webComponents = js.context['WebComponents'];
+  var logFlags = (webComponents == null || webComponents['flags'] == null) ? {}
+      : webComponents['flags']['log'];
   if (logFlags == null) logFlags = {};
   var loggers =
       [_observeLog, _eventsLog, _unbindLog, _bindLog, _watchLog, _readyLog];