update polymer js to 0.4.0

pkg/polymer/test/template_distribute_dynamic_test.dart

Index: pkg/polymer/test/template_distribute_dynamic_test.dart
diff --git a/pkg/polymer/test/template_distribute_dynamic_test.dart b/pkg/polymer/test/template_distribute_dynamic_test.dart
index d808419da4cbed3e9191ba23bf53ae59ef522766..4b57a193be17d6620b166188b333e666c1b6efb2 100644
--- a/pkg/polymer/test/template_distribute_dynamic_test.dart
+++ b/pkg/polymer/test/template_distribute_dynamic_test.dart
@@ -39,15 +39,7 @@ class XTest extends PolymerElement {
           'shadowDOM dynamic distribution via template');
       expect(children[2].text, 'bar', reason:
           'shadowDOM dynamic distribution via template');
-
-      // TODO(jmesserly): restore this if we get the JS interop capability.
-      /*
-      if (window.ShadowDOMPolyfill) {
-        var actualChildren = this.$.echo.impl.children;
-        chai.assert.equal(actualChildren.length, 4,
-          'shadowDOMPolyfill distributes expected number of actual children.');
-      }
-      */
+      expect(children.length, 3, reason: 'expected number of children');
     });
   }
 }