Fixing Element.shadowRoot to work with webkitShadowRoot

tests/html/shadowroot_test.dart

Index: tests/html/shadowroot_test.dart
diff --git a/tests/html/shadowroot_test.dart b/tests/html/shadowroot_test.dart
index 56cf13b5c0d62864a9105c2008c703a5c66e3dc7..04e0b5e2c8ad92ed5930fda1264273166de3dd35 100644
--- a/tests/html/shadowroot_test.dart
+++ b/tests/html/shadowroot_test.dart
@@ -18,8 +18,10 @@ main() {
 
     // If it's supported, then it should work. Otherwise should fail.
     if (isSupported) {
-      var shadowRoot = new DivElement().createShadowRoot();
+      var div = new DivElement();
+      var shadowRoot = div.createShadowRoot();
       expect(shadowRoot, isShadowRoot);
+      expect(div.shadowRoot, shadowRoot);
     } else {
       expect(() => new DivElement().createShadowRoot(), throws);
     }