Replace bootstrap logic with 'boot.js', use 'component/dart' mime-type and add

pkg/polymer/test/property_observe_test.dart

Index: pkg/polymer/test/property_observe_test.dart
diff --git a/pkg/polymer/test/property_observe_test.dart b/pkg/polymer/test/property_observe_test.dart
index c3facc6576271b55bec8c6838e685bbd7dd03316..6fe6a2bfe843b9f2ec08e411fb976cac17cb08ac 100644
--- a/pkg/polymer/test/property_observe_test.dart
+++ b/pkg/polymer/test/property_observe_test.dart
@@ -82,10 +82,11 @@ class XTest2 extends XTest {
   }
 }
 
-main() => initPolymer().run(() {
+@initMethod
+main() {
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
 
   test('changes detected', () => _done.future);
-});
+}