Bring back initPolymer, allow boot.js only if using "polymer_experimental.html".

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 af73a20718bccb3ee7b8e01143e314b7cdfd9296..64389066331046cb5c3e91c74d3b65074da5eb58 100644
--- a/pkg/polymer/test/template_distribute_dynamic_test.dart
+++ b/pkg/polymer/test/template_distribute_dynamic_test.dart
@@ -52,11 +52,10 @@ class XTest extends PolymerElement {
   }
 }
 
-@initMethod
-main() {
+main() => initPolymer().run(() {
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
 
   test('inserted called', () => (querySelector('x-test') as XTest).onTestDone);
-}
+});